Process for the preparation of an optical compensatory sheet comprising cellulose ester film, orientation layer, and optically anisotropic layer formed of liquid crystal molecules having a fixed alignment

ABSTRACT

An optical compensatory sheet comprises a cellulose ester film, an orientation layer and an optically anisotropic layer formed of liquid crystal molecules in this order. Alignment of the liquid crystal molecules is fixed. An alkaline solution is coated on a surface of the cellulose ester film to saponify the surface. The saponified surface is coated with a coating solution of the orientation layer.

FIELD OF INVENTION

The present invention relates to an optical compensatory sheetcomprising a cellulose ester film, an orientation layer and an opticallyanisotropic layer formed of liquid crystal molecules in this order, inwhich alignment of the liquid crystal molecules is fixed. The inventionalso relates to a process for preparation of the optical compensatorysheet. The invention further relates to a polarizing plate and a liquidcrystal display using the optical compensatory sheet.

BACKGROUND OF INVENTION

A liquid crystal display generally comprises a liquid crystal cell, apolarizing plate and an optical compensatory sheet (phase retarder). Ina display of transmission type, two polarizing plates are placed on bothsides of the liquid crystal cell, and the optical compensatory sheet isprovided between the cell and one or each of the polarizing plates. Onthe other hand, a display of reflection type comprises a reflectionboard, a liquid crystal cell, one optical compensatory sheet and onepolarizing plate, in this order.

The liquid crystal cell comprises a pair of substrates, rod-like liquidcrystal molecules and an electrode layer. The rod-like liquid crystalmolecules are provided between the substrates, and the electrode layerhas a function of applying a voltage to the rod-like liquid crystalmolecules. According to alignment of the rod-like liquid crystalmolecules in the cell, various display modes have been proposed.Examples of the display modes for transmission type include TN (twistednematic) mode, IPS (in-plane switching) mode, FLC (ferroelectric liquidcrystal) mode, OCB (optically compensatory bend) mode, STN (supertwisted nematic) mode and VA (vertically aligned) mode. Examples of themodes for reflection type include HAN (hybrid aligned nematic) mode.

The polarizing plate generally comprises a pair of transparentprotective films and a polarizing membrane provided between them. Forpreparing the polarizing membrane, a polyvinyl alcohol film is soakedwith aqueous solution of iodine or a dichromatic dye, and is thenuniaxially stretched.

The optical compensatory sheet is generally provided in various liquidcrystal displays, to prevent displayed images from undesirable coloringand to enlarge a viewing angle of the liquid crystal cell. As theoptical compensatory sheet, a stretched birefringent polymer film hasbeen conventionally used.

Recently, in place of the stretched birefringent polymer film, anoptical compensatory sheet comprising a transparent support and athereon provided optically anisotropic layer formed from liquid crystalmolecules (particularly, discotic liquid crystal molecules) has beenproposed. The optically anisotropic layer is formed through the steps ofaligning the liquid crystal molecules and then fixing the alignment. Asthe liquid crystal molecules, liquid crystal molecules havingpolymerizable groups are generally used. For fixing the alignment, theyare polymerized. The liquid crystal molecules give large birefringenceand have various alignment forms, and accordingly an opticalcompensatory sheet obtained from the liquid crystal molecules has aspecific optical character that cannot be obtained from the conventionalstretched birefringent polymer film.

The optical character of the optical compensatory sheet is designedaccording to that of the liquid crystal cell, namely, according todisplay mode of the liquid crystal cell. In fact, if an opticalcompensatory sheet is made with liquid crystal molecules (particularly,discotic liquid crystal molecules), various optical characteristics canbe realized according to the display mode of the liquid crystal cell.

Various optical compensatory sheets using discotic liquid crystalmolecules have been proposed according to liquid crystal cells ofvarious display modes. For example, the optical compensatory sheet forliquid crystal cell of TN mode is described in Japanese PatentProvisional Publication No. 6(1994)-214116, U.S. Pat. Nos. 5,583,679,5,646,703 and German Patent Publication No. 3,911,620A1. Thecompensatory sheet for liquid crystal cell of IPS or FLC mode isdescribed in Japanese Patent Provisional Publication No. 10(1998)-54982.The compensatory sheet for OCB or HAN mode is described in U.S. Pat. No.5,805,253 and International Patent Application No. WO96/37804. Thecompensatory sheet for STN mode is described in Japanese PatentProvisional Publication No. 9(1997)-26572. The compensatory sheet for VAmode is described in Japanese Patent No. 2,866,372.

In the optical compensatory sheet comprising a transparent support and athereon-provided optically anisotropic layer formed from liquid crystalmolecules, an orientation layer for controlling the alignment of liquidcrystal molecules is provided between the support and the anisotropiclayer. As the transparent support, a cellulose ester film is preferablyused. In preparing the optical compensatory sheet, it is necessary tofix the orientation layer (normally, made of polyvinyl alcohol) closelyon the cellulose ester film (transparent support).

However, the affinity between the cellulose ester film and polyvinylalcohol (material of the orientation layer) is so poor that theinterface is easily cracked or broken, and hence the opticallyanisotropic layer on the orientation layer easily comes off from thefilm (support). Particularly when the optical compensatory sheet is cut(or punched out) to size for the display, the orientation layer(together with the optically anisotropic layer) is shocked and therebyoften partly peeled from the film. At that time, fragments of the peeledorientation layer (and the peeled optically anisotropic layer) arescattered and dusted on the film, and consequently cause “undesirablebrilliant points” in a displayed image. The term “undesirable brilliantpoints” means defects undesirably sparking on a screen of liquid crystaldisplay. In order to avoid the undesirable brilliant points (i.e., inorder to enhance the adhesion between the cellulose ester film and theorientation layer), the cellulose ester film has been immersed in analkaline solution to saponify the surface of the film or otherwise anundercoating layer made of gelatin has been provided on the film.Japanese Patent Provisional Publication No. 8(1996)-94838 describessaponification treatments of the cellulose ester film.

SUMMARY OF INVENTION

If the cellulose ester film is immersed in an alkaline solution so thatthe surface may be saponified enough to enhance the adhesion between thefilm and the orientation layer, not only the aimed surface but also theopposite surface is saponified at the same time. Therefore, when thethus-treated film is wound up into a roll, the top surface often sticksto the bottom surface in the roll. In addition, the process of immersingfor saponification is hardly carried out simultaneously with the step ofapplying hydrophilic material (such as the coating solution for formingthe orientation layer), and hence the immersing process must beperformed independently of the coating for forming the orientationlayer. As a result, the saponification treatment relatively costs a lot.

On the other hand, for providing a gelatin-undercoating layer on thecellulose ester film to enhance the adhesion between the film and theorientation layer, a coating solution for forming the undercoating layeris generally used. The coating solution contains a solvent in whichcellulose ester is easily swollen (e.g., a ketone), and hence oftenimpairs smoothness of the film surface even though the adhesion betweenthe film and the orientation layer is improved. As a result, stripedunevenness is liable to appear in the longitudinal direction of thefilm, and accordingly causes unevenness of displaying to make thequality of displayed images worse when the film is used in a liquidcrystal display.

As described above, it has been wanted to improve the adhesion betweenthe cellulose ester film and the orientation layer without any trouble(for example, without sticking of the film in a roll) while the filmsurface is kept smooth.

It is an object of the present invention to provide an opticalcompensatory sheet having an excellent surface and having an orientationlayer fixed closely on a support film with improved adhesion.

Also, it is another object of the invention to provide a process forpreparation of the above compensatory sheet.

Further, it is a further object of the invention to provide a polarizingplate in which the above compensatory sheet is unified with a polarizingmembrane.

Furthermore, it is a furthermore object of the invention to provide aliquid crystal display comprising the above compensatory sheet andthereby improved in avoiding unevenness of displaying and undesirablebrilliant points.

The present invention provides an optical compensatory sheet comprisinga cellulose ester film, an orientation layer and an opticallyanisotropic layer formed of liquid crystal molecules in this order,alignment of said liquid crystal molecules being fixed, wherein analkaline solution is coated on a surface of the cellulose ester film tosaponify the surface, and wherein the saponified surface is coated witha coating solution of the orientation layer.

The invention also provides a process for preparation of an opticalcompensatory sheet comprising a cellulose ester film, an orientationlayer and an optically anisotropic layer formed of liquid crystalmolecules in this order, alignment of said liquid crystal moleculesbeing fixed, wherein the process successively comprises the steps of:coating an alkaline solution on a surface of the cellulose ester film;washing the surface to remove the alkaline solution; coating a coatingsolution of the orientation layer on the washed surface; and drying thecoating solution to form the orientation layer.

The invention further provides a polarizing plate comprising twotransparent protective films and a polarizing membrane placed betweenthe protective films, wherein one of the protective films is an opticalcompensatory sheet comprising a cellulose ester film, an orientationlayer and an optically anisotropic layer formed of liquid crystalmolecules in this order, alignment of said liquid crystal moleculesbeing fixed, wherein an alkaline solution is coated on a surface of thecellulose ester film to saponify the surface, and wherein the saponifiedsurface is coated with a coating solution of the orientation layer.

The invention furthermore provides a liquid crystal display having twopolarizing plates and a liquid crystal cell provided between the plates,wherein the polarizing plate comprises two transparent protective filmsand a polarizing membrane placed between the protective films, andwherein at least one of the two protective films placed between theliquid crystal cell and the polarizing membranes is an opticalcompensatory sheet comprising a cellulose ester film, an orientationlayer and an optically anisotropic layer formed of liquid crystalmolecules in this order, alignment of said liquid crystal moleculesbeing fixed, wherein an alkaline solution is coated on a surface of thecellulose ester film to saponify the surface, and wherein the saponifiedsurface is coated with a coating solution of the orientation layer.

In the present specification, the term “essentially at 45°” means thenoticed angle is in the range of the strict angle±5°. The allowance ispreferably less than ±4°, more preferably less than ±3°, most preferablyless than ±2°. The term “slow axis” means the direction giving themaximum refractive index. The term “fast axis” means the directiongiving the minimum refractive index. The term “transmission axis” meansthe directions giving the maximum transmittance.

The present inventors have succeeded in providing an opticalcompensatory sheet having an excellent surface and having an orientationlayer fixed closely on a support film with improved adhesion. Thecompensatory sheet comprises a cellulose ester film as the support, andonly one surface of the film is selectively saponified. For theselective saponification, an alkaline solution is applied on the aimedsurface of the film.

Since the saponification treatment is performed through a coatingprocedure, only the aimed surface is selectively saponified so that theadhesion between the film and the orientation layer can be improvedwithout troubles such as sticking of the film in a roll. In addition,since it is not necessary to provide a gelatin-undercoating layer, thefilm surface can be kept smooth.

Further, since it takes relatively short time to perform the coatingprocedure for saponification, the saponification procedure can becarried out successively after the coating solution for forming theorientation layer is applied. Consequently, the production cost of theoptical compensatory sheet is lowered.

In producing a polarizing plate in which the compensatory sheet isunified with a polarizing membrane, the polarizing membrane-facingsurface of the cellulose ester film can be also selectively saponifiedthrough the coating procedure. This means that the conventionalimmersing saponification treatment can be omitted and accordingly thatthe productivity can be improved to lower the production cost.

A TFT liquid crystal display of TN mode is often equipped with a unifiedelliptically polarizing plate in which the transparent support of theoptical compensatory sheet comprising liquid crystal molecules serves asone of the protective films for the polarizing plate. That liquidcrystal display thermally deforms, and is liable to give an image withleaked light. The thermal deformation changes optical characters of theoptical compensatory sheet, and consequently causes the light-leakage.Particularly, a film of polymer having hydroxyl groups (such as acellulose ester film) is largely affected by the environmentalconditions. For reducing the light-leakage caused by the thermaldeformation, the inventors have found that it is effective to lower thephoto-elasticity of the optical compensatory sheet and particularly tothin down the cellulose ester film.

However, the inventors have also found that it is difficult to handlethe thin cellulose ester film when the gelatin-undercoating layer isprovided through a coating procedure.

If the optical compensatory sheet is produced according to the processof the invention, it is not necessary to provide thegelatin-undercoating layer. Accordingly, the process of the invention isalso effective in producing the thin optical compensatory sheet havingexcellent planeness.

Further, the process for selectively saponifying only one surface of thecellulose ester film is yet also effective in producing the protectivefilm of the polarizing plate.

DETAILED DESCRIPTION OF INVENTION

(Optical Character of Cellulose Ester Film)

The optical character of cellulose ester film is controlled according tothe mode (kind) of liquid crystal cell on which the resultant opticalcompensatory sheet is provided.

If the cellulose ester film is required to have optical anisotropy, itpreferably exhibits high retardation.

The film may be stretched to control (increase) the retardation value inthe plane (Re retardation value).

On the other hand, the retardation value along the thickness (Rthretardation value) can be controlled (increased) (1) with aretardation-increasing agent or (2) through the cooling dissolutionmethod. If the cellulose ester film is made of cellulose acetate, theRth value can be controlled by the average acetic acid content(acetylation degree). Since the retardation values can be thusincreased, the cellulose ester film (which has been conventionallyregarded as an optically isotropic film) can be used as an opticallyanisotropic film having an optically compensatory function. In fact, thethus-prepared optically anisotropic cellulose ester film can opticallycompensate the liquid crystal cell cooperatively with the opticalanisotropic layer provided thereon.

The optically anisotropic cellulose ester film has an Re retardationvalue preferably in the range of −50 to 50 nm, more preferably in therange of −20 to 20 nm.

The Rth retardation value of the anisotropic cellulose ester film ispreferably in the range of 60 to 1,000 nm.

The retardation value in the plane (Re) is a product of thebirefringence in the plane and the thickness of the film, and that alongthe thickness (Rth) is a product of the birefringence in the thicknessdirection and the thickness of the film. The concrete Re value can beobtained by measurement in which an incident ray (e.g., ray emitted fromHe-Ne laser [wavelength: 632.8 nm]) is perpendicularly applied onto thefilm surface, and the concrete Rth value can be obtained by measurementin which incident rays (e.g., rays emitted from He-Ne laser [wavelength:632.8 nm]) are obliquely applied onto the film surface. In themeasurement, an ellipsometer (e.g., M-150, JASCO COOPORATION) is used toobtain data, which are then extrapolated to find the retardation values.

The retardation values in the plane (Re) and along the thickness (Rth)are calculated according to the following formulas (1) and (2),respectively.Re=(nx−ny)×d  (1)Rth=[{(nx+ny)/2}−nz]×d.  (2)In the formulas, nx is a refractive index along the slow axis in thefilm plane, ny is a refractive index along the fast axis in the filmplane, nz is a refractive index in the thickness direction of the film,and d is the thickness of the film in terms of nm.(Cellulose Ester)

The cellulose ester has a (viscosity average) polymerization degree ofpreferably 200 to 700, more preferably 250 to 550, most preferably 250to 350. The viscosity average polymerization degree can be measured withan Ostwald's viscometer. Form the measured specific viscosity [η], theviscosity average polymerization degree DP is calculated according tothe formula: DP=[η]/Km in which Km is a constant 6×10⁻⁴.

The cellulose ester may be prepared only from virgin flakes, but wastesof used cellulose ester films are preferably mixed to reuse. The amountof the wastes is in the range of 3 to 95 wt. %, preferably in the rangeof 6 to 80 wt. %, more preferably in the range of 10 to 70 wt. %.

As the cellulose ester, cellulose esters of lower fatty acids arepreferred. The term “lower fatty acids” means fatty acids having 6 orless carbon atoms. The number of carbon atoms is preferably 2 (celluloseacetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Celluloseacetate is particularly preferred, and cellulose esters of mixed fattyacids such as cellulose acetate propionate and cellulose acetatebutyrate are also usable.

The average acetic acid content (acetylation degree) of celluloseacetate is preferably in the range of 55.0 to 62.5%. In consideration ofthe film properties, the average acetic acid content is more preferablyin the range of 58.0 to 62.5%. However, the film of cellulose acetatehaving an average acetic acid content of 55.0 to 58.0% (preferably 57.0to 58.0%) exhibits a high retardation value along the thickness.

(Retardation-Increasing Agent)

A retardation-increasing agent may be incorporated into the celluloseester film, to increase the retardation value along the thickness. Asthe retardation-increasing agent, an aromatic compound having amolecular structure in which at least two aromatic rings are includedand their conformations do not suffer steric hindrance can be used.

The aromatic compound is added in an amount of 0.01 to 20 weight parts,preferably in an amount of 0.05 to 15 weight parts, more preferably inan amount of 0.1 to 10 weight parts, based on 100 weight parts of thecellulose ester. Two or more aromatic compounds may be used incombination.

The term “an aromatic ring” means not only an aromatic hydrocarbon ringbut also an aromatic heterocyclic ring.

As the aromatic hydrocarbon ring, a six-membered ring (namely, a benzenering) is particularly preferred.

The aromatic heterocyclic ring is generally unsaturated. The aromaticheterocyclic ring is preferably a five-, six- or seven-membered ring,and more preferably a five- or six-membered ring. The aromaticheterocyclic ring generally has double bonds as many as possible. Thehetero atom in the ring preferably is nitrogen atom, sulfur atom oroxygen atom, and more preferably is nitrogen atom. Examples of thearomatic heterocyclic ring include furan ring, thiophene ring, pyrrolering, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring,imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring,pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring and1,3,5-triazine ring.

The retardation-increasing agent preferably has a molecular weight of300 to 800. The boiling point of the retardation-increasing agent ispreferably 260° C. or more. The boiling point can be measured by meansof a commercially available apparatus (e.g., TG/DTA100, SEIKOInstruments Inc.).

Concrete examples of the retardation-increasing agent are described inJapanese Patent Provisional Publication Nos. 2000-111914, 2000-275434and PCT/JP 00/02619.

(Preparation of Cellulose Ester Film)

The cellulose ester film in the invention is preferably preparedaccording to the solvent cast method. In the solvent cast method, asolution (dope) in which the polymer is dissolved in an organic solventis used. The organic solvent preferably contains a main solvent selectedfrom the group consisting of an ether having 3 to 12 carbon atoms, aketone having 3 to 12 carbon atoms, an ester having 3 to 12 carbon atomsand a halogenated hydrocarbon having 1 to 7 carbon atoms.

The ether, the ketone or the ester may have a cyclic structure. Acompound having two or more functional groups of ether, ketone and ester(—O—, —CO— and —COO—) is also usable as the solvent. The organic solventmay have other functional groups such as alcoholic hydroxyl. If thesolvent is the compound having two or more functional groups, the numberof carbon atoms is in any of the above ranges.

Examples of the ether having 3 to 12 carbon atoms include diisopropylether, dimethoxymethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran,anisole and phenetol.

Examples of the ketone having 3 to 12 carbon atom include acetone,methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone,cyclohexanone and methylcyclohexanone.

Examples of the ester having 3 to 12 carbon atoms include ethyl formate,propyl formate, pentyl formate, methyl acetate, ethyl acetate, andpentyl acetate.

Examples of the compounds having two or more functional groups include2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

A representative halogenated hydrocarbon having 1 to 7 carbon atoms ismethylene chloride. From the technical viewpoint, the halogenatedhydrocarbon such as methylene chloride can be used without any problem.However, in consideration of the global environment and workingconditions, the organic solvent preferably contains essentially nohalogenated hydrocarbon. This means that the organic solvent preferablycontains halogenated hydrocarbon in an amount of less than 5 wt. % (morepreferably less than 2 wt. %). Also preferably, halogenated hydrocarbonsuch as methylene chloride is not found in the resultant film at all.

Two or more organic solvents can be used in combination. It isparticularly preferred to use a mixture of at least three differentkinds of solvents. The first solvent is preferably selected from thegroup consisting of a ketone having 3 or 4 carbon atoms, an ester having3 or 4 carbon atoms, and a mixture thereof. The second solvent ispreferably selected from the group consisting of a ketone having 5 to 7carbon atoms, an acetoacetic ester, and a mixture thereof. The thirdsolvent is preferably selected from the group consisting of an alcoholhaving a boiling point of 30 to 170° C., a hydrocarbon having a boilingpoint of 30 to 170° C., and a mixture thereof.

Examples of the ketone and the ester usable as the first solvent includeacetone, methyl acetate, methyl formate, and ethyl formate.

Examples of the second solvent include cyclopentanone, cyclohexanone,and methyl acetylacetate.

The third solvent is preferably selected from the group consisting of analcohol having a boiling point of 30 to 170° C., a hydrocarbon having aboiling point of 30 to 170° C., and a mixture thereof. The alcohol ispreferably monohydric. The hydrocarbon moiety of the alcohol may have astraight-chain structure, a branched-chain structure, or a cyclicstructure. The hydrocarbon moiety of the alcohol is preferably asaturated aliphatic hydrocarbon. The alcohol may be primary, secondaryor tertiary. Examples of the alcohol include methanol (boiling point:64.65° C.), ethanol (b.p.: 78.325° C.), 1-propanol (b.p.: 97.15° C.),2-propanol (b.p.: 82.4° C.), 1-butanol (b.p.: 117.9° C.), 2-butanol(b.p.: 99.5° C.), t-butanol (b.p.: 82.45° C.), 1-pentanol (b.p.: 137.5°C.), 2-methyl-2-butanol (b.p.: 101.9° C.), and cyclohexanol (b.p.: 161°C.). These alcohols are preferably used in a combination of two or more.The hydrocarbon may have a straight-chain structure, a branched-chainstructure, or a cyclic structure. The hydrocarbon may be eitheraliphatic or aromatic. The hydrocarbon may be either saturated orunsaturated. Examples of the hydrocarbon include cyclohexane (boilingpoint: 80.7° C.), hexane (b.p.: 69° C.), benzene (b.p.: 80.1° C.),toluene (b.p.: 110.6° C.), and xylene (b.p.: 138.4 to 144.4° C.).

The mixed solvent of the above three different kinds of solventspreferably contains the first solvent, the second solvent and the thirdsolvent in amounts of 30 to 95 wt. %, 1 to 40 wt. %, and 1 to 40 wt. %,respectively. The content of the first solvent is more preferably in therange of 40 to 90 wt. %, further preferably in the range of 50 to 90 wt.%, and most preferably in the range of 50 to 85 wt. %. The content ofeach of the second and third solvents is more preferably in the range of3 to 30 wt. %. Examples of the ratio among the solvents and celluloseester in the dope are as follows:

cellulose ester/methyl acetate/cyclohexanone/methanol/ethanol=X/(70−X)/20/5/5 (by weight),

cellulose ester/methyl acetate/methyl ethylketone/acetone/methanol/ethanol=X/(50−X)/20/20/5/5 (by weight),

cellulose ester/acetone/methyl acetoacetate/ethanol=X/(75−X)/20/5 (byweight),

cellulose ester/methylacetate/cyclopentanone/methanol/ethanol=X/(80−X)/10/5/5 (by weight),

cellulose ester/methylacetate/1,3-dioxolane/methanol/ethanol=X/(70−X)/20/5/5 (by weight),

cellulose ester/methylacetate/dioxane/acetone/methanol/ethanol=X/(60−X)/20/10/5/5 (by weight),and

cellulose ester/methyl acetate/1,3-dioxolane/cyclohexanone/methyl ethylketone/methanol/ethanol=X/(55−X)/20/10/7.5/7.5 (by weight).

In the above, X represents the amount of cellulose ester in terms ofweight part and is preferably in the range of 10 to 25, more preferablyin the range of 15 to 23.

Besides the above solvents, the dope (cellulose ester solution) forforming the cellulose ester film may contain fluoro-alcohol or methylenechloride in an amount of 10 wt. % or less based on the total weight ofthe organic solvents, in order to improve the transparency of the filmand to make the cellulose ester more quickly dissolved in the dope.

The fluoro-alcohol has a boiling point of preferably 165° C. or less,more preferably 111° C. or less, most preferably 80° C. or less. Thefluoro-alcohol has preferably 2 to 10, more preferably 2 to 8 carbonatoms. The fluoro-alcohol is a fluorine-containing aliphatic alcoholthat may have a substituent group. Examples of the substituent groupinclude an aliphatic group that may contain fluorine and an aromaticgroup.

Examples of the fluoro-alcohol include 2-fluoroethanol (boiling point:103° C.), 2,2,2-trifluoroethanol (b.p.: 80° C.),2,2,3,3-tetrafluoro-1-propanol (b.p.: 109° C.), 1,3-difluoro-2-propanol(b.p.: 55° C.), 1,1,1,3,3,3-hexa-2-methyl-2-propanol (b.p.: 62° C.),1,1,1,3,3,3-hexafluoro-2-propanol (b.p.: 59° C.),2,2,3,3,3-pentafluoro-1-propanol (b.p.: 80° C.),2,2,3,4,4,4-hexafluoro-1-butanol (b.p.: 114° C.),2,2,3,3,4,4,4-heptafluoro-1-butanol (b.p.: 97° C.),perfluoro-tert-butanol (b.p.: 45° C.),2,2,3,3,4,4,5,5-octfluoro-1-pentanol (b.p.:142° C.),2,2,3,3,4,4-hexafluoro-1,5-pentanediol (b.p.: 111.5° C.),3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1-octanol (b.p.: 95° C.),2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluoro-1-octanol (b.p.: 165° C.),1-(pentafluorophenyl)ethanol (b.p.: 82° C.), and2′,3,4,5,6-pentafluorobenzyl alcohol (b.p.: 115° C.). Two or morefluoro-alcohols may be mixed to use in combination.

The cellulose ester solution (dope) is prepared according to the coolingdissolution method or the high-temperature dissolution method.

The cooling dissolution method is explained below.

At the first stage of the cooling dissolution method, cellulose ester isgradually added to the main solvent and stirred at room temperature (−10to 40° C.). If the main solvent is a mixture consisting of two or moresolvent components, the cellulose ester may be dissolved in the mixture.Otherwise, the cellulose ester may be dissolved in one of the solventcomponents and then other solvent components may be added to prepare themixture. For example, after the cellulose ester is swollen with agelling solvent such as alcohol, the other solvent components are added.If so, the cellulose ester can be prevented from inhomogeneousdissolution. Thus, a mixture of organic solvent and cellulose ester isprepared.

The amount of cellulose ester in the mixture is preferably in the rangeof 10 to 40 wt. %, more preferably in the range of 10 to 30 wt. %.Various additives described below may be added in the mixture.

The prepared mixture is then cooled to a temperature of −100 to −10° C.,preferably −80 to −10° C., more preferably −50 to −20° C., mostpreferably −50 to −30° C. The cooling procedure can be carried out, forexample, with dry ice-methanol bath (−75° C.) or with cooled ethyleneglycol solution (−30 to −20° C.). Through the cooling procedure, themixture is solidified. There is no particular restriction on the coolingrate. If the cooling procedure is carried out in a batchwise operation,the viscosity of the mixture increases according as it is gettingcolder. The more viscous the mixture becomes, the worse the coolingefficiency becomes. Accordingly, the pot in which the mixture is chargedmust have such an excellent cooling efficiency that the aimed coolingtemperature can be realized. The aimed cooling temperature can beachieved in a short time by means of a generally used cooling apparatus.

The cooling rate is preferably 4° C./minute or more, more preferably 8°C./minute or more, and most preferably 12° C./minute or more. Thecooling rate is preferably as fast as possible. However, a theoreticalupper limit of the cooling rate is 10,000° C./second, a technical upperlimit is 1,000° C./second, and a practical upper limit is 100°C./second. The cooling rate means the change of temperature at thecooling step per the time taken to complete the cooling step. The changeof temperature means the difference between the temperature at which thecooling step is started and the temperature at which the cooling step iscompleted.

The cooled mixture is then warmed to a temperature of 0 to 200° C.,preferably 0 to 150° C., more preferably 0 to 120° C., most preferably 0to 50° C. Through the warming procedure, the cellulose ester isdissolved in the organic solvent. For warming, the mixture may be leftat room temperature or may be heated in a warm bath.

The warming rate is 4° C./minute or more, more preferably 8° C./minuteor more, and most preferably 12° C./minute or more. The warming rate ispreferably as fast as possible. However, a theoretical upper limit ofthe cooling rate is 10,000° C./second, a technical upper limit is 1,000°C./second, and a practical upper limit is 100° C./second. The warmingrate means the change of temperature at the warming step per the timetaken to complete the warming step. The change of temperature means thedifference between the temperature at which the warming step is startedand the temperature at which the warming step is completed.

The warming procedure may be performed under a pressure of 0.3 to 30Mpa. If so, the procedure can be completed in a relatively short time.The time is preferably in the range of 0.5 to 60 minutes, morepreferably in the range of 0.5 to 2 minutes.

Thus, a homogeneous solution can be prepared. If the cellulose ester isnot sufficiently dissolved, the cooling and warming procedures may berepeated. It can be judged by observation with the eyes whether thecellulose ester is sufficiently dissolved or not.

In the process of cooling dissolution method, a sealed vessel ispreferably used to prevent contamination of water, which may be causedby dew condensation at the cooling step. Further, the mixture may becooled under an elevated pressure and warmed under a reduced pressure sothat the time taken to complete the cooling and warming steps can beshortened, and hence a vessel resisting pressure is preferably used toconduct the procedure under an elevated or reduced pressure.

The cellulose ester solution (dope) can be also prepared according tothe high-temperature dissolution method.

In the high-temperature dissolution method, cellulose ester is graduallyadded to the main solvent and stirred at room temperature (−10 to 40°C.). If the main solvent is a mixture consisting of two or more solventcomponents, the cellulose ester may be dissolved in the mixture.Otherwise, the cellulose ester may be dissolved in one of the solventcomponents and then other solvent components may be added to prepare thecellulose ester mixture. For example, after the cellulose ester isswollen with a gelling solvent such as alcohol, the other solventcomponents are added. If so, the cellulose ester can be prevented frominhomogeneous dissolution.

Prior to the preparation of the cellulose ester mixture, the celluloseester is preferably beforehand swollen with the mixed organic solvent ora gelling solvent such as alcohol. For example, the cellulose ester isstirred and gradually added to the solvent at a temperature of −10 to40° C., or otherwise the cellulose ester is swollen with one solventcomponent and then other solvent components are mixed, to prepare ahomogeneous swollen mixture. The cellulose ester may be swollen with twoor more solvent components, and then other solvent components may bemixed to prepare the swollen mixture. The thus-prepared swollen mixturemay be mixed in the main solvent to prepare a mixed solution.

The mixed solution preferably contains the cellulose ester in an amountof 40 wt. % or less. In consideration of drying efficiency in formingthe film, the content of cellulose ester is as high as possible. Thecontent of cellulose ester is adjusted so that the resultant dopecontains the cellulose ester in an amount of 10 to 40 wt. %. Theresultant dope preferably contains the cellulose ester in a highcontent. However, if the cellulose ester is so thickly contained thatthe viscosity of the dope increases, troubles are liable to occur informing the film. Accordingly, the content of cellulose ester in theresultant dope is preferably in the range of 15 to 30 wt. %, morepreferably in the range of 17 to 25 wt. %.

In the high-temperature dissolution method, a sealed vessel is used inorder to prevent the solvent from evaporation. Further, the swellingprocedure may be performed under a reduced or elevated pressure toshorten the time to complete the procedure. For the procedure under areduced or elevated pressure, a vessel resisting pressure is used.

The thus-obtained cellulose ester mixture is then heated to 70 to 240°C. (preferably, 80 to 220° C., more preferably 100 to 200° C., mostpreferably 100 to 190° C.) under an elevated pressure of 0.2 to 30 Mpa.During this heating procedure under an elevated pressure, the mixture ispreferably stirred. Thus, a solution in which cellulose ester ishomogeneously dissolved is obtained.

There is no particular restriction on the methods for heating andelevating the pressure. For example, after the mixture is charged in avessel, the pressure in the vessel can be elevated by introducing aninert gas into the vessel, or by heating and evaporating the solvent toincrease the vapor pressure.

The vessel is preferably heated from outside. For example, a jacketheater is preferably used. Otherwise, liquid heated with a plate-heaterplaced outside of the vessel may be circulated through a pipe woundaround the vessel, to heat the whole vessel.

The mixture is preferably stirred with a propeller mixer provided in thevessel. The wing of the propeller preferably has a length reaching theinside wall of the vessel. Further, at the tip of the wing, a scratchingmean is preferably provided to scratch and renew the liquid attached onthe inside wall.

The heated mixture must be cooled to a temperature below the lowest ofthe boiling points of the solvent components. For cooling the mixture,the vessel may be left at room temperature or preferably cooled withcooling water.

The above warming and cooling procedures may be repeated to promote thedissolution of cellulose ester. It can be judged by observation with theeyes whether the cellulose ester is sufficiently dissolved or not.

In preparing the cellulose ester solution, the vessel may be filled withan inert gas such as nitrogen gas. The viscosity of cellulose acetatesolution immediately before the film-forming process is adjusted so thatthe solution can be cast to form the film, and is normally in the rangeof 10 to 2,000 ps·s, preferably in the range of 30 to 400 ps·s. If thesolution is prepared according to the high-temperature dissolutionmethod under an elevated pressure, a sealed vessel is used to preventthe solvent from evaporation. Further, the swelling procedure may beperformed under a reduced or elevated pressure to shorten the time tocomplete the procedure. For the procedure under a reduced or elevatedpressure, a pressure-resisting vessel or a pressure-resisting productionline is indispensable.

From the thus-prepared cellulose ester solution, the film is formed. Thefilm-forming procedure may be performed according to the conventionalsolvent cast method by means of a common apparatus.

At the first stage of the film-forming procedure, the prepared dope(cellulose ester solution) is settled in a storing tank to removebubbles.

The dope is then sent to a pressure-die by means of, for example, aconstant-pressure gear pump, which can send the dope in an amountprecisely controlled by rotation of the gear. From the pressure-die, thedope is evenly cast onto an endlessly running support. When the supportturns around almost once and the releasing point appears, the half-drieddope film (referred to as “web”) is peeled. Both sides of the web wereheld with clips to keep the width, and the web is dried and transferredwith a tenter. The web is then wound up in a predetermined length bymeans of a winding machine. The apparatus for the solvent cast method isoften equipped with a coating means by which additional layers such as asubbing layer, an anti-static layer, an anti-halation layer and aprotective film are provided on the film surface. Examples of thefilm-forming procedure are described below, but they by no meansrestrict the invention.

According to the solvent cast method, the prepared cellulose estersolution (dope) is cast on a drum or a band, and the solvent isevaporated to form a film. The solid content of the dope is preferablycontrolled in the range of 10 to 40%. The surface of the drum or band ispreferably beforehand polished to be a mirror. The casting and dryingsteps of the solvent cast method are described in U.S. Pat. Nos.2,336,310, 2,367,603, 2,492,078, 2,492,977, 2,492,978, 2,607,704,2,739,069, 2,739,070, British Patent Nos. 640,731, 736,892, JapanesePatent Publication Nos. 45(1970)-4554, 49(1974)-5614, Japanese PatentProvisional Publication Nos. 60(1985)-176834, 60(1985)-203430 and62(1987)-115035. The surface temperature of the drum or band ispreferably 10° C. or below.

The dope may be singly cast onto a support such as the drum or the band,to form a single layer. Otherwise, two or more dopes may be prepared,and from them two or more layers may be formed to prepare a layeredfilm.

In the case where two or more cellulose ester solutions arecooperatively cast, two or more nozzles are arranged at intervals alongthe running direction of the support, and from each nozzle each polymersolution is cast to form a layered film (Japanese Patent ProvisionalPublication Nos. 61(1986)-158414, 1(1989)-122419 and 11(1999)-198285).Otherwise, polymer solutions may be cast from two nozzles to form a film(Japanese Patent Publication No. 60(1985)-27562, Japanese PatentProvisional Publication Nos. 61(1986)-94724, 61(1986)-947245,61(1986)-104813, 61(1986)-158413 and 6(1994)-134933). Further, a flow ofhigh-viscous polymer solution may be enclosed with a flow of low-viscousone to form a layered flow, and the high- and low-viscous solutions inthe layered flow may be simultaneously extruded to produce a film(Japanese Patent Provisional Publication No. 56(1981)-162617).

Further, the method disclosed in Japanese Patent Publication No.44(1969)-20235 may be adopted. In the disclosed process, a dope is caston the support from one nozzle to form a film. After peeled from thesupport, the formed film is turned over and again placed on the support.On the thus appearing surface (having been in contact with the support),another dope is cast from another nozzle to form a film.

The used cellulose ester solutions may be the same or different fromeach other. The function of each formed cellulose ester layer can begiven by each corresponding solution extruded from each nozzle.

Other functional layers (e.g., adhesive layer, dye layer, antistaticlayer, anti-halation layer, UV absorbing layer, polarizing layer) can besimultaneously formed together with the cellulose ester layer.

In a conventional single layer preparation process, it is necessary toextrude a cellulose ester solution having such high concentration andsuch high viscosity that the resultant film may have the aimedthickness. Accordingly, that solution is often so unstable that solidcontents are deposited to cause troubles and to impair the planeness. Toavoid the problem, plural concentrated solutions are simultaneouslyextruded from nozzles onto the support. The thus-prepared thick film hasexcellent planeness. In addition, since the concentrated solutions areused, the film is so easily dried that the productivity (particularly,production speed) can be improved.

(Additives)

A plasticizer can be added into the dope to enhance mechanical strengthof the resultant film or to shorten the time for drying. The plasticizeris, for example, a phoshate ester or a carbonate ester. Examples of thephosphate ester used as the plasticizer include triphenyl phosphate(TPP) and tricresyl phosphate (TCP). Typical examples of the carbonateester are phthalate esters and citrate esters. Examples of the phthalateesters include dimethyl phthalate (DMP), diethyl phthalate (DEP),dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate(DPP) and diethylhexyl phthalate (DEHP). Examples of the citrate estersinclude triethyl o-acetylcitrate (OACTE) and tributyl o-acetylcitrate(OACTB). Besides the above, butyl oleate, methylacetyl ricinolate,dibutyl sebacate and various trimellitic esters are also usable. Theplasticizers of phosphate esters (DMP, DEP, DBP, DOP, DPP, DEHP) arepreferred. Particularly preferred are DEP and DPP.

The content of the plasticizer is preferably in the range of 0.1 to 25wt. %, more preferably in the range of 1 to 20 wt. %, most preferably inthe range of 3 to 15 wt. % based on the amount of cellulose ester.

Further, a deterioration inhibitor (e.g., oxidation inhibitor, peroxidedecomposer, radical inhibitor, metal inactivating agent, oxygenscavenger, amine) may be incorporated in the cellulose ester film. Thedeterioration inhibitor is described in Japanese Patent ProvisionalPublication Nos. 3(1991)-199201, 5(1993)-1907073, 5(1993)-194789,5(1993)-271471 and 6(1994)-107854. The content of the deteriorationinhibitor is preferably in the range of 0.01 to 1 wt. %, more preferablyin the range of 0.01 to 0.2 wt. % based on the amount of the dope. Ifthe content is less than 0.01 wt. %, the deterioration inhibitor giveslittle effect. If the content is more than 1 wt. %, the inhibitor oftenoozes out (bleeds out) to appear on the surface of the film.Particularly preferred deterioration inhibitors are butylatedhydroxytoluene (BHT) and tribenzylamine (TBA). Japanese PatentProvisional Publication No. 7(1995)-11056 describes UV absorbers.

A cellulose acetate having an average acetic acid content of 55.0 to58.0 is inferior to one having an average acetic acid content of 58.0 ormore in the stability of the prepared dope and in the properties of theresultant film. However, these defects can be essentially cancelled outwith the aforementioned deterioration inhibitor, particularly butylatedhydroxytoluene (BHT).

(Stretching Procedure)

The cellulose ester film is preferably stretched at least in onedirection parallel to the film surface. Preferably, the film isstretched in the longitudinal direction (MD) or in the lateral direction(TD). The stretching may be longitudinally uniaxial, laterally uniaxial,or in a combination thereof (i.e., multi-axial). The stretching(extension) ratio is in the range of 1 to 2, preferably in the range of1 to 1.8, more preferably in the range of 1 to 1.6. The film immediatelybefore stretching contains the solvent in an amount of 0 to 50 wt. %.For the longitudinal stretching, the content of the solvent ispreferably in the range of 0 to 10 wt. %, more preferably in the rangeof 0 to 5 wt. %. For the lateral stretching, the content is preferablyin the range of 5 to 45 wt. %, more preferably in the range of 10 to 40wt. %.

(1) Longitudinal Stretching

The longitudinal stretching can be performed by means of two series ofnipping rolls arranged at intervals. The rolls near the outlet are madeto rotate more quickly than those near the inlet, to stretch the filmlongitudinally. The stretching speed is preferably in the range of 50 to1,000%/minute, more preferably in the range of 80 to 800%/minute, mostpreferably in the range of 100 to 700%/minute. The temperature at whichthe film is stretched (hereinafter, referred to as “stretchingtemperature) is preferably in the range of Tg (glass transitiontemperature of the film)−120° C. to Tg+50° C., more preferably in therange of Tg−110° C. to Tg+30° C. For heating the film, the film may bemade to contact with a heating roll, stretched in a thermostatic bath,or exposed to an IR or halogen heater. These heating means may be usedin combination.

For preventing the film from wrinkling, the film is preferably preheatedbefore stretching and gradually cooled after stretching. The film may bepreheated either stepwise or continuously. In the stepwise preheating,the film is heated and kept for 1 second to 3 minutes at one or moretemperatures between room temperature and the stretching temperature,and then heated to the stretching temperature. In the continuouspreheating, the film is continuously heated from room temperature to thestretching temperature at a rate of 10 to 1,000° C./minute. It is alsopreferred to combine these preheating methods. The heated film afterstretched is gradually cooled from the stretching temperature to roomtemperature. The film may be cooled either stepwise or continuously. Inthe stepwise cooling, the film is cooled and kept for 1 second to 3minutes at one or more temperatures between the stretching temperatureand room temperature, and then cooled to room temperature. In thecontinuous cooling, the film is continuously cooled from the stretchingtemperature to room temperature at a rate of −10 to −1,000° C./minute.It is also preferred to combine these cooling methods. Further, toimprove the film surface, the film is preferably subjected to additionalstretching at an extension ratio of 0 to 10%. In contrast, it is alsopreferred to relax the film at a ratio of 0 to 10%.

(2) Lateral Stretching

For laterally stretching the film, the film may be widened with clipsbeforehand attached onto both sides of the film. The stretching speed ispreferably in the range of 5 to 300%/minute, more preferably in therange of 10 to 200%/minute, most preferably in the range of 15 to150%/minute. The stretching temperature is preferably in the range of Tg(glass transition temperature of the film)−120° C. to Tg+50° C., morepreferably in the range of Tg−110° C. to Tg+30° C. For heating the film,the film is preferably stretched in a thermostatic bath (tenter method).The film may be stretched either at one stretching temperature or at twoor more temperatures. For stretching the film at two or moretemperatures, the tenter is divided into two or more parts in whichstretching temperatures are individually set.

For preventing the film from wrinkling, the film is preferably preheatedbefore stretching and gradually cooled after stretching. The film may bepreheated either stepwise or continuously. In the stepwise preheating,the film is heated and kept for 1 second to 3 minutes at one or moretemperatures between room temperature and the stretching temperature,and then heated to the stretching temperature. In the continuouspreheating, the film is continuously heated from room temperature to thestretching temperature at a rate of 10 to 1,000° C./minute. It is alsopreferred to combine these preheating methods. The heated film afterstretched is gradually cooled from the stretching temperature to roomtemperature. The film may be cooled either stepwise or continuously. Inthe stepwise cooling, the film is cooled and kept for 1 second to 3minutes at one or more temperatures between the stretching temperatureand room temperature, and then cooled to room temperature. In thecontinuous cooling, the film is continuously cooled from the stretchingtemperature to room temperature at a rate of −10 to −1,000° C./minute.It is also preferred to combine these cooling methods. Further, toimprove the film surface, the film is preferably subjected to additionalstretching at an extension ratio of 0 to 10%. In contrast, it is alsopreferred to relax the film at a ratio of 0 to 10%.

(Dimension of Film)

The thickness of the film is preferably in the range of 20 to 500 μm,more preferably in the range of 20 to 300 μm, further preferably in therange of 30 to 200 μm, most preferably in the range of 35 to 150 μm. Thewidth is preferably in the range of 0.4 to 4 m, more preferably in therange of 0.5 to 3 m, most preferably in the range of 0.6 to 2 m. Neareach side edge of the film, a knurl is preferably provided. The knurledposition is preferably in the area of 5 to 30 mm, preferably 7 to 20 mmfrom the edge. The height of the knurl is preferably 10 to 100 μm, morepreferably 20 to 80 μm. For forming the knurl, the film is pressedeither from one or both of the top and the bottom.

(Saponification Treatment)

An alkaline solution is applied on one surface of the cellulose esterfilm so that only the surface on which the orientation layer is to beprovided may be selectively saponified. As the coating method, knownmethods such as dip-coating, curtain-coating, extrusion coating,bar-coating and E type coating can be adopted. If the dip coating isadopted, the opposite surface (which is not to be saponified) is maskedbefore the film is dipped in the alkaline solution.

The solvent of the alkaline solution (coating solution forsaponification) is preferably excellent in wettability with thecellulose ester film, and also preferably hardly swells out the film(namely, hardly makes the film surface rough). As the solvent, alcoholsare preferred. Particularly, monohydric or dihydric alcohols having 1 to5 carbon atoms are preferred. Examples of the alcohols include ethylalcohol, normal-propyl alcohol, iso-propyl alcohol, normal-butylalcohol, iso-butyl alcohol, tert-butyl alcohol and ethylene glycol. Aparticularly preferred alcohol is iso-propyl alcohol. Two or morealcohols may be mixed to use. The solvent may contain water in an amountof 0 to 50 wt. %, preferably 0 to 30 wt. %, and more preferably 0 to 15wt. %. An aqueous solution of surface-active agent can be used as thesolvent.

An alkali well-soluble in the above solvent is preferably used in thesolution. As the alkali, KOH and NaOH are particularly preferred. Thealkaline solution has a pH value of preferably 10 or more, morepreferably 12 or more.

In order to saponify well, the surface is made to keep coated with thealkaline solution preferably for 1 second to 5 minutes, more preferablyfor 2 seconds to 1 minute, most preferably for 3 seconds to 30 seconds.The surface is then preferably washed with water, and dried. Thetemperature at which the film is saponified is preferably in the rangeof 10 to 80° C., more preferably in the range of 15 to 60° C., mostpreferably in the range of 20 to 40° C.

In the invention, the cellulose ester film is preferably saponifiedunder a reduced oxygen gas atmosphere. The oxygen gas concentration inthe atmosphere is in the range of 0 to 18%, preferably in the range of 0to 15%, more preferably in the range of 0 to 10%. If the alkalinesolution is applied under such atmosphere, the surface properties of thefilm can be controlled to enhance the adhesion to the orientation layer.The gas component other than oxygen gas in the atmosphere is preferablyan inert gas. Examples of the inert gas include nitrogen, helium, andargon. Nitrogen is particularly preferred.

After saponifying the film, the alkaline solution is washed away withwashing liquid. The temperature of the washing liquid is preferably inthe range of 30 to 80° C., more preferably in the range of 35 to 70° C.,most preferably in the range of 40 to 65° C. The cellulose ester filmcoated with the alkaline solution may be immersed in a washing liquidbath, or otherwise the washing liquid may be sprayed onto the film. Thewashing liquid may be water, and may contain other solvents in an amountof 0 to 50% (preferably 0 to 20%). Examples of the solvents includealcohols having 5 or less carbon atoms. Particularly preferably, thewashing liquid is pure water. After washed, the film is dried at 40 to200° C., preferably 50 to 150° C., more preferably 60 to 120° C.

Successively after the film surface is saponified, the orientation layercan be provided in the manner described after. According to theinvention, only one surface of the cellulose ester film can beselectively saponified. Therefore, even if the film in which theorientation layer is provided on the saponified surface is wound up intoa roll, the surface of the orientation layer by no means sticks onto thebottom surface (surface on which the orientation layer is not provided).

(Surface Properties of Cellulose Ester Film)

The saponification by applying the alkaline solution reduces“undesirable brilliant points” or “unevenness of displaying”. However,the inventors have found that, for surely avoiding “undesirablebrilliant points”, it is necessary to control the surface properties ofthe saponified film surface. In other wards, even if the film surface issaponified, “undesirable brilliant points” cannot be fully reducedwithout controlling the surface properties. Further, it is also foundthat, if a liquid crystal display comprising the film having asaponified surface whose properties are not controlled is used for along time, “fogs” are often observed in a displayed image.

The term “undesirable brilliant points” means defects sparking on ascreen of liquid crystal display, and hence the defects are easilyobserved when a dark image is displayed. According to the inventors'study, the brilliant points are caused by dust attached on theorientation layer or on the optically anisotropic layer. It is alsofound that the dust is formed when the optical compensatory sheet is cut(or punched out) to size for the display. Because of shock in cutting orpunching out the sheet, the orientation layer (together with theoptically anisotropic layer) is slightly peeled from the film to formthe dust.

The term “fogs” means foggy defects on the screen, and hence they areeasily observed when a white image is displayed. The fogs hardly appearimmediately after the display is produced, but often appear after thedisplay is used for a long time. According to the inventors' study, alow-molecular weight compound (e.g., plasticizer) contained in thecellulose ester film (used as the optical compensatory sheet) isgradually deposited for a long time at the interface between theorientation layer and the optically anisotropic layer to cause the fogs.It is also found that the fogs are more liable to be caused in the casewhere the film is coated with the alkaline solution than in the casewhere the film is immersed in the alkaline solution bath forsaponifying.

It is further found that, if the surface saponified by coating satisfiesat least one (preferably, two or more) of the following conditions (1)to (5), not only the merits of the coating saponification are fullygiven (for example, the surface can be kept smooth) but also theundesirable brilliant points can be avoided without causing the fogswhen the optical compensatory sheet is used in a liquid crystal display.

The surface conditions for preventing the cellulose ester filmsaponified by coating from “undesirable brilliant points” and “fogs” areas follows:

(1) the saponification depth at the surface is in the range of 0.010 to0.8 μm (preferably in the range of 0.020 to 0.6 μm, more preferably inthe range of 0.040 to 0.4 μm);

(2) at the surface, the ratio between numbers of chemical bonds C═O perC—O (C═O/C—O) is in the range of 0 to 0.6 (preferably in the range of 0to 0.55, more preferably in the range of 0 to 0.5), while the ratio ofC—C per C—O (C—C/C—O) is in the range of 0.45 to 0.75 (preferably in therange of 0.5 to 0.7, more preferably in the range of 0.5 to 0.65);

(3) if the cellulose ester film contains a phosphorus-containingcompound as the plasticizer, the ratio between contents of elements Oper C (O/C) at the surface is in the range of 0.62 to 0.75 (preferablyin the range of 0.63 to 0.73, more preferably in the range of 0.64 to0.71), while the ratio of P per C (P/C) is in the range of 0.007 to0.015 (preferably in the range of 0.008 to 0.0145, more preferably inthe range of 0.009 to 0.014);

(4) the contact angle with water is in the range of 20° to 55°(preferably in the range of 25° to 50°, more preferably in the range of30° to 45°); and

(5) if the cellulose ester film is made of cellulose acetate, the degreeof acetyl substitution at the surface is in the range of 1.8 to 2.7(preferably in the range of 1.85 to 2.5, more preferably in the range of1.9 to 2.4).

It is not clearly known why the surface satisfying the above conditionsis free from the undesirable brilliant points and fogs, but is assumedbelow.

If the saponification depth is too deep, the main chain of celluloseester positioned near the surface is cut so that the molecular weight islowered to impair the mechanical strength and accordingly to deterioratethe adhesion between the film and the orientation layer. Further, sincethe film surface is excess (and deeply) saponified, much amount oflow-molecular weight compound (e.g., plasticizer) comes out andprecipitates on the surface. The low-molecular weight compound furthercomes out for a long time onto the surface of the orientation layer, tocause fogs.

On the other hand, if the saponification depth is too shallow, the filmis so insufficiently saponified that the adhesion between the film andthe orientation layer is lowered. Further, since the saponificationdepth is extremely shallow, a little amount of low-molecular weightcompound (e.g., plasticizer) positioned near the surface is liable tocome out and precipitate for a long time on the surface of theorientation layer.

The condition of coating saponification is controlled so that thecellulose ester film may satisfy the above surface conditions. It isvery important to coat the film with the alkaline solution under a lowoxygen atmosphere of 18% or less and to wash the alkaline solution witha liquid (preferably, hot water) at a temperature of 30° C. to 80° C.The process for saponification is described after in detail togetherwith the production process of optical compensatory sheet.

(Evaluation of Surface Properties)

The surface properties of cellulose ester film are described below.

(1) Saponification Depth at Film Surface

While the surface of the film is being subjected to ion etching, theamount of elements specific to the alkali used for the saponification ismeasured according to the photoelectron spectroscopy (XPS). From theobtained etching time, the saponification depth is calculated on thebasis of the data of a standard sample.

(Preparation of Standard Sample)

To 10 weight parts of triacetyl cellulose, 5 weight parts of colloidalsilica is added. The obtained mixture is dissolved in a mixed solvent of90 weight parts of dichloromethane and 10 weight parts of methanol. Thesolution is applied on a cellulose ester film (e.g., a commerciallyavailable film, Fujitac) to form a layer having approx. 0.2 μm thickness(dry condition). After the layer is dried, the thickness is againmeasured by means of a thickness meter to determine the thickness (t) interms of μm. Thus, a standard sample is prepared.

(Calculation of Saponification Depth)

The standard sample is etched by means of a photoelectron spectrometer(ESCA750, Shimadzu Seisakusho Ltd., acceleration voltage: 2 kV,acceleration current: 20 mA) under an argon gas atmosphere of 5×10⁻⁴ Pa.While the etching is performed for 2 minutes, the signal of Si-2p ismeasured. The measurement is repeated, and the total etching time (T)elapsing until the intensity of the signal weakens to 1/10 of that ofthe first measurement is determined. From t/T (μm/minute), the etchingrate is determined. Based on that, the saponification depth of thetested sample is calculated.

(Evaluation of Saponification Depth at Surface of Tested Sample)

The cellulose ester film is coated with an alkaline solution tosaponify. Immediately after the alkaline solution remaining on thesurface is wiped with filter paper, the film is frozen with liquidnitrogen and then freeze-dried to fix the alkali penetrated into thefilm. In the same manner as the standard sample, the thus-treated filmis subjected to the XPS measurement while being etched to evaluate thesaponification depth. The element to be detected in the XPS is thatspecific to the alkali. Namely, if NaOH or KOH is used for thesaponification, the signal of Na or K is measured, respectively. Whilethe etching is performed for 2 minutes, the signal is measured. Themeasurement is repeated, and the total etching time elapsing until theintensity of the signal weakens to 1/10 of that of the first measurementis determined. From t/T (μm/minute), the etching rate is determined.Based on the etching time, the saponification depth of the tested sampleis calculated.

(2) Ratios of Chemical Bonds C═O/C—O and C—C/C—O Existing on FilmSurface

After saponified, washed and dried, the cellulose ester film issubjected to the XPS measurement with the photoelectron spectrometer(ESCA750, Shimadzu Seisakusho Ltd.). Form the obtained spectrum, theratios C═O/C—O and C—C/C—O are evaluated through the following steps.

i) A spectrum assigned to C_(1s) is measured in the bonding energy rangeof 295 to 280 eV.

ii) In the spectrum, a line that connects the minimum point in the rangeof 295 to 293 eV and that in the range of 282 to 280 eV is drawn todetermine the base line.

iii) The amount of C—O is estimated from the maximum intensity (based onthe base line) in the spectrum of C_(1s) since the bonding energy givingthe maximum intensity corresponds to that of C—O.

The bonding energy higher than that of C—O by 2.1 eV corresponds to thatof C═O, and hence the intensity at that bonding energy represents theamount of C═O.

The bonding energy lower than that of C—O by 1.4 eV corresponds to thatof C—C, and hence the intensity at that bonding energy represents theamount of C—C.

From the thus-obtained intensities, the ratios of chemical bonds C═O/C—Oand C—C/C—O existing on the film surface are evaluated.

(3) Ratios of Elements O/C and P/C Existing on Film Surface

After saponified, washed and dried, the cellulose ester film issubjected to the XPS measurement with the photoelectron spectrometer(ESCA750, Shimadzu Seisakusho Ltd.). Form the obtained spectra, theratios O/C and P/C are evaluated through the following steps.

i) A spectrum assigned to C_(1s) is measured in the bonding energy rangeof 295 to 280 eV. In the measured spectrum, a line that connects theminimum point in the range of 295 to 293 eV and that in the range of 282to 280 eV is drawn to determine the base line, and the area bounded bythe base line and the spectrum is measured to determine the value X(cps·eV).

ii) Another spectrum assigned to O_(1s) is measured in the bondingenergy range of 540 to 526 eV. In the measured spectrum, a line thatconnects the minimum point in the range of 540 to 538 eV and that in therange of 528 to 526 eV is drawn to determine the base line, and the areabounded by the base line and the spectrum is measured. The value of themeasured area is then divided by the ionization cross section (2.85) todetermine the value Y (cps·eV).

iii) Sill another spectrum assigned to P_(2p) is measured in the bondingenergy range of 145 to 125 eV. In the measured spectrum, a line thatconnects the average intensity in the range of 143 to 141 eV and that inthe range of 129 to 127 eV is drawn to determine the base line, and thearea bounded by the base line and the spectrum is measured. The value ofthe measure area is then divided by the ionization cross section (1.25)to determine the value Z (cps·eV).

iv) Finally, the ratios Y/X and Z/X are calculated to estimate those ofelements O/C and P/C, respectively.

(4) Contact Angle with Water

After saponified, washed and dried, the cellulose ester film is left for3 hours under the conditions of 25° C. (temperature) and 60% (humidity).The contact angle with water is then measured by means of a contactangle meter (CA-A, KYOWA INTERFACE SCIENCE CO., LTD.).

(5) Acetic Acid Content at Film Surface

According to the ATR-IR method, the acetic acid content at the filmsurface is measured through the following steps.

i) After saponified, washed and dried, the cellulose ester film issubjected to the ATR-IR measurement in which the incident angle iscontrolled at 45° by means of a Ge prism.

ii) In the obtained IR spectrum, a line that connects the minimumabsorption point in the range of 1,450 to 1,550 cm⁻¹ and that in therange of 1,350 to 1,300 cm⁻¹ is drawn to determine the base line, andthe absorption intensity (based on the base line) in the range of1,360±20 cm⁻¹ is measured to determine the maximum absorption I. On theother hand, another line that connects the minimum absorption point inthe range of 1,200 to 1,100 cm⁻¹ and that in the range of 900 to 800cm⁻¹ is drawn to determine the base line, and the absorption intensity(based on the base line) in the range of 1,150±20 cm⁻¹ is measured todetermine the maximum absorption i. The ratio of I/i is then calculated.

iii) Finally, assuming that the I/i ratios are 0.5 and 4.7 when theacetic acid contents are 0 and 3, respectively, the relation between theacetic acid content and the I/i is linearly approximated to estimate theacetic acid content at the film surface from the above-obtained I/i.

(Orientation Layer)

Examples of the orientation layer include a layer of an organic compound(preferably polymer) subjected to rubbing treatment, an obliquelydeposited layer of an inorganic compound, and a layer having microgrooves. Further, a built-up film formed according to Langmuir-Blodgetttechnique (LB technique) from ω-tricosanoic acid,dioctadecyldimethylammoniumchloride or methyl stearate can be used asthe orientation layer. In addition, a layer prepared by orientingdielectric materials by application of electric field or magnetic fieldcan be employed as the orientation layer. The polymer layer subjected tothe rubbing treatment is particularly preferred. The rubbing treatmentis performed by rubbing the surface of the layer several times withpaper or cloth along a certain direction.

The polymer for forming the orientation layer is selected according tothe displaying mode of liquid crystal cell. For example, for a liquidcrystal cell in which rod-like liquid crystal molecules are essentiallyvertically aligned (e.g., cell of VA, OCB or HAN mode), the polymer isselected so that the orientation layer may essentially horizontallyalign liquid crystal molecules in the optically anisotropic layer. Incontrast, if most of the rod-like liquid crystal molecules in the cellare essentially horizontally aligned (e.g., cell of STN mode), thepolymer is selected so that the orientation layer may essentiallyvertically align liquid crystal molecules in the optically anisotropiclayer. For a cell in which most of the rod-like liquid crystal moleculesare essentially obliquely aligned (e.g., cell of TN mode), the polymeris selected so that the orientation layer may essentially obliquelyalign liquid crystal molecules in the optically anisotropic layer.

Examples of the polymer are described in the aforementioned publicationsin which various optical compensatory sheets using discotic liquidcrystal molecules are proposed according to liquid crystal cells ofvarious display modes.

The polymer may be cross-linked to reinforce the orientation layer. Forexample, cross-linking groups are introduced and then made to react tocross-link the polymer. Japanese Patent Provisional Publication No.8(1996)-338913 describes the cross-linking of the polymer for formingthe orientation layer.

The thickness of the orientation layer is preferably in the range of0.01 to 5 μm, more preferably in the range of 0.05 to 1 μm.

(Optically Anisotropic Layer)

The optically anisotropic layer is formed from liquid crystal molecules.

As the liquid crystal molecules, rod-like or discotic molecules arepreferred. Discotic liquid crystal molecules are particularly preferred.

Examples of the rod-like liquid crystal compound include azomethines,azoxys, cyanobiphenyls, cyanophenyl esters, benzoic esters,cyclohexanecarboxylate phenyl esters, cyanophenylcyclohexanes,cyano-substituted phenylpyrimidines, alkoxy-substitutedphenylpyrimidines, phenyldioxanes, tolanes, andalkenylcyclohexylbenzonitriles. Not only low-molecular weight liquidcrystal compounds like the above but also polymer liquid crystalcompounds can be used. The polymer liquid crystal compounds compriseside chains corresponding to the low-molecular weight liquid crystalcompounds like the above. Japanese Patent Provisional Publication No.5(1993)-53016 discloses an optical compensatory sheet using the polymerliquid crystal compound.

The discotic liquid crystal compounds are described in variouspublications (e.g., C. Destrade et al., Mol. Cryst. vol. 71, pp. 111,(1981); “Chemistry of Liquid crystal (Japanese)”, Kagaku-Sosetsu,22(1994), Chapters 5 and 10 (section 2); B. Kohn et al., Angew. Chem.Soc. Chem. Comm., pp. 1794, (1985); and J. Zhang et al., J. Am. Chem.Soc. vol. 116, pp.2655, (1994)). Japanese Patent Provisional PublicationNo. 8(1996)-27284 describes polymerization of discotic liquid crystals.

A polymerizable group should be bound to a discotic core of the discoticcompound to cause the polymerization reaction and thereby to fix thediscotic liquid crystal molecules. However, if the polymerizable groupis directly bound to the discotic core, it is difficult to keep thealignment at the polymerization reaction. Therefore, a linking group isintroduced between the discotic core and the polymerizable group.Accordingly, the discotic liquid crystal compound having a polymerizablegroup preferably is represented by the following formula (I).D(-L-P)_(n)  (I)in which D is a discotic core; L is a divalent linking group; P is apolymerizable group; and n is an integer of 4 to 12.

Examples of the discotic cores (D) are shown below. In the examples, LP(or PL) means the combination of the divalent linking group (L) and thepolymerizable group (P).

In the formula (I), the divalent linking group (L) preferably isselected from the group consisting of an alkylene group, an alkenylenegroup, an arylene group, —CO—, —NH—, —O—, —S— and combinations thereof.The L more preferably is a divalent linking group comprising at leasttwo divalent groups selected from the group consisting of an alkylenegroup, an alkenylene group, an arylene group, —CO—, —NH—, —O— and —S—.The L most preferably is a divalent linking group comprising at leasttwo divalent groups selected from the group consisting of an alkylenegroup, an alkenylene group, an arylene group, —CO— and —O—. The alkylenegroup preferably has 1 to 12 carbon atoms. The alkenylene grouppreferably has 2 to 12 carbon atoms. The arylene group preferably has 6to 10 carbon atoms. The alkylene group, the alkenylene group and thearylene group may have substituent groups (e.g., alkyl groups, halogenatoms, cyano, alkoxy groups, acyloxy groups).

Examples of the divalent linking groups (L) are shown below. In theexamples, the left side is attached to the discotic core (D), and theright side is attached to the polymerizable group (P). The AL means analkylene group or an alkenylene group. The AR means an arylene group.

-   L1: -AL-CO—O-AL--   L2: -AL-CO—O-AL-O—-   L3: -AL-CO—O-AL-O-AL--   L4: -AL-CO—O-AL-O—CO—-   L5: —CO-AR—O-AL--   L6: —CO-AR—O-AL-O—-   L7: —CO-AR—O-AL-O—CO—-   L8: —CO—NH-AL--   L9: —NH-AL-O—-   L10: —NH-AL-O—CO—-   L11: —O-AL--   L12: —O-AL-O—-   L13: —O-AL-O—CO—-   L14: —O-AL-O—CO—NH-AL--   L15: —O-AL-S-AL--   L16: —O—CO-AL-AR—O-AL-O—CO—-   L17: —O—CO-AR—O-AL-CO—-   L18: —O—CO-AR—O-AL-O—CO—-   L19: —O—CO-AR—O-AL-O-AL-O—CO—-   L20: —O—CO-AR—O-AL-O-AL-O-AL-O—CO—-   L21: —S-AL--   L22: —S-AL-O—-   L23: —S-AL-O—CO—-   L24: —S-AL-S-AL--   L25: —S-AR-AL-

For compensating a cell in which rod-like liquid 5 crystal molecules areoriented in twisted alignment (e.g., cell of STN mode), the discoticliquid crystal molecules are preferably also oriented in twistedalignment. If the above AL (alkylene or alkenylene group) has anasymmetric carbon, the discotic liquid crystal molecules can be spirallyoriented in twisted alignment. Otherwise, it can also orient thediscotic molecules spirally in twisted alignment to incorporate anoptical active compound having an asymmetric carbon (namely, a chiralagent) into the optically anisotropic layer.

The polymerizable group (P) in the formula (I) is determined accordingto the polymerization reaction. Examples of the polymerizable groups (P)are shown below.

The polymerizable group (P) preferably is an unsaturated polymerizablegroup (P1 to P7), an epoxy group (P8) or an aziridyl group (P9), morepreferably is an unsaturated polymerizable group, and most preferably isan ethylenically unsaturated group (P1 to P6).

In the formula (I), n is an integer of 4 to 12, which is determinedaccording to the chemical structure of the discotic core (D). The 4 to12 combinations of L and P can be different from each other. However,the combinations are preferably identical.

Two or more discotic liquid crystal compounds may be used incombination. For example, the aforementioned polymerizable discoticliquid crystal compound and non-polymerizable one can be used incombination.

The non-polymerizable discotic liquid crystal compound is preferably acompound in which the polymerizable group in the aforementionedpolymerizable liquid crystal compound is replaced with a hydrogen atomor an alkyl group. In other wards, the non-polymerizable discotic liquidcrystal compound is preferably represented by the following formula(II).D(-L-R)_(n)  (II)in which D is a discotic core; L is a divalent linking group; R is ahydrogen atom or an alkyl group; and n is an integer of 4 to 12.

Examples of the discotic cores (D) in the formula (II) are the same asthose shown above except that the LP (or PL) is replaced with LR (orRL). Examples of the divalent linking groups (L) in the formula (II) arealso the same as those shown above.

The alkyl group of R has preferably 1 to 40, more preferably 1 to 30carbon atoms. A chain alkyl group is preferred to a cyclic one, and astraight chain alkyl group is particularly preferred. The R isparticularly preferably a hydrogen atom or a straight chain alkyl grouphaving 1 to 30 carbon atoms.

For providing the optically anisotropic layer, a coating solutioncontaining the liquid crystal molecules, the following polymerizationinitiator and optional additives (e.g., plasticizer, monomer, surfaceactive agent, cellulose ester, 1,3,5-triazine compound, chiral agent) isapplied on the orientation layer.

As the solvent for preparing the coating solution, organic solvents arepreferred. Examples of the organic solvents include amides (e.g.,N,N-dimethyl formamide), sulfoxides (e.g., dimethyl sulfoxide),heterocyclic compounds (e.g., pyridine), hydrocarbons (e.g., benzene,hexane), alkyl halides (e.g., chloroform, dichloromethane), esters(e.g., methyl acetate, butyl acetate), ketones (e.g., acetone, methylethyl ketone), and ethers (e.g., tetrahydrofuran, 1,2-dimethoxyethane).Alkyl halides and ketones are preferred. Two or more organic solventsare preferably used in combination.

The coating solution is applied according to the known method (e.g.,extrusion-coating, direct gravure coating, reverse gravure coating,dip-coating).

The liquid crystal molecules are preferably essentially homogeneouslyaligned. More preferably, the molecules are fixed with the homogeneousalignment maintained. Most preferably, the homogeneously alignedmolecules are polymerized to fix.

The polymerization reaction can be classified into a thermal reactionwith a thermal polymerization initiator and a photo-reaction with aphoto polymerization initiator. The photo polymerization reaction ispreferred.

Examples of the photo polymerization initiators include α-carbonylcompounds (described in U.S. Pat. Nos. 2,367,661, 2,367,670), acyloinethers (described in U.S. Pat. No. 2,448,828), α-hydrocarbon substitutedacyloin compounds (described in U.S. Pat. No. 2,722,512), polycyclicquinone compounds (described in U.S. Pat. Nos. 2,951,758, 3,046,127),combinations of triarylimidazoles and p-aminophenyl ketones (describedin U.S. Pat. No. 3,549,367), acridine or phenazine compounds (describedin Japanese Patent Provisional Publication No. 60(1985)-105667 and U.S.Pat. No. 4,239,850) and oxadiazole compounds (described in U.S. Pat. No.4,212,970).

The amount of the photo polymerization initiator is preferably in therange of 0.01 to 20 wt. %, and more preferably in the range of 0.5 to 5wt. % based on the solid content of the coating solution.

The light irradiation for the photo polymerization is preferablyconducted with ultraviolet rays.

The exposure energy is preferably in the range of 20 to 50,000 mJ/cm²,more preferably in the range of 100 to 800 mJ/cm². The light irradiationcan be conducted while the layer is heated to accelerate the photopolymerization reaction.

The thickness of the optically anisotropic layer is preferably in therange of 0.1 to 10 μm, more preferably in the range of 0.5 to 5 μm, mostpreferably in the range of 1 to 5 μm. However, for some modes of liquidcrystal cells, thick optically anisotropic layers (thickness: 3 to 10μm) may be provided.

As described above, how the liquid crystal molecules are aligned in theoptically anisotropic layer is determined according to the displayingmode of liquid crystal cell. The alignment of liquid crystal moleculesis controlled by what kind of liquid crystal compound is used, what kindof orientation layer is provided, and what additives (e.g., plasticizer,binder, surface active agent) are incorporated.

(Surface Treatment of Optical Compensatory Sheet)

In the case where the optical compensatory sheet is unified with apolarizing membrane to produce a polarizing plate, the membrane-facingsurface of the sheet may be subjected to a surface treatment to enhancethe adhesion between the sheet and the membrane. Examples of the surfacetreatment include corona discharge treatment, glow discharge treatment,flame treatment, acid treatment, alkali treatment, and ultraviolet (UV)treatment.

In the corona or glow discharge treatment, the surface of the opticalcompensatory sheet is exposed to discharge. The discharge treatment canbe carried out by means of a commercially available discharge treatmentapparatus.

The discharge treatment is preferably performed in the presence ofaqueous vapor. The partial pressure of aqueous vapor is preferably inthe range of 10 to 100%, more preferably in the range of 40 to 90%,based on the total pressure. Prior to the discharge treatment, thecellulose ester film is preferably preheated. The temperature ofpreheating is preferably 50° C. or more, more preferably 70° C. or more,most preferably 80° C. or more. The upper limit of the temperatureis-the glass transition point of the cellulose ester film.

The glow discharge treatment is carried out under a degree of vacuumpreferably in the range of 0.005 to 20 Torr, more preferably in therange of 0.02 to 2 Torr. The voltage for performing the glow dischargetreatment is preferably in the range of 500 to 5,000 V, more preferablyin the range of 500 to 3,000 V. The frequency of the glow discharge ispreferably in the range of 50 Hz to 20 MHz, more preferably in the rangeof 1 KHz to 1 MHz. The intensity of the glow discharge is preferably inthe range of 0.01 to 5 KV·A·minute/m², more preferably in the range of0.15 to 1 KV·A·minute/m².

Immediately after the discharge treatment is completed, the opticalcompensatory sheet is preferably cooled.

In performing the flame treatment, it is important to control the mixingratio between gas (natural gas, propane gas) and air. The volume ratioof gas/air is preferably in the range of 1/13 to 1/21, more preferablyin the range of 1/14 to 1/20. The heat quantity applied to the celluloseester film is preferably in the range of 1 to 50 kcal/m². The film ispreferably positioned so that the gap between the film and the top ofinner flame may be 4 cm or less.

For performing the acid or alkali treatment, the optical compensatorysheet is immersed in an acidic or alkaline aqueous solution,respectively.

Acid for the acid treatment is preferably an inorganic acid such ashydrochloric acid, sulfuric acid or nitric acid. Alkali for the alkalitreatment is preferably a hydroxide of alkali metal such as sodiumhydroxide or potassium hydroxide. The immersing time is preferably inthe range of 30 seconds to 10 minutes. After immersed in the solution,the film is washed with water.

Particularly preferably, the acid or alkali treatment is performedthrough a coating procedure in the same manner as that subjected to theorientation layer-facing surface of the cellulose ester film.

In the ultraviolet (UV) treatment, the polarizing membrane-facingsurface of the optical compensatory sheet is exposed to ultravioletrays.

The wavelength of the ultraviolet rays is preferably in the range of 220to 380 nm. The exposure energy is preferably in the range of 20 to10,000 mJ/cm², more preferably in the range of 50 to 2,000 mJ/cm², andmost preferably in the range of 100 to 1,500 mJ/cm².

(Transparent Protective Film)

As the transparent protective film of the polarizing plate, a polymerfilm is used. The term “transparent” means that the polymer film has alight-transmittance of 80% or more. The transparent protective film isnormally made of cellulose ester, preferably acetyl cellulose. Thecellulose ester film is preferably formed according to the solvent castmethod. The thickness of the protective film is preferably in the rangeof 20 to 500 μm, more preferably in the range of 50 to 200 μm.

For improving the adhesion to the polarizing membrane, the protectivefilm is preferably subjected to one or more of the aforementionedvarious surface treatments. In performing the saponification treatment,the treatment is preferably carried out by coating.

(Polarizing Plate)

The polarizing plate comprises a pair of transparent protective filmsand a polarizing membrane provided between them. The polarizing membraneis, for example, a stretched film of hydrophilic polymer (e.g.,partially saponified copolymer of ethylene-vinyl acetate, partiallyformalized polyvinyl alcohol, polyvinyl alcohol) adsorbing iodine ordichromatic dye. Otherwise, a plastic film (e.g., a polyvinyl chloridefilm) treated to align the polyene is also usable as the polarizingmembrane.

If the optical compensatory sheet of the invention is used as one of thetransparent protective films in the polarizing plate, an excellent(elliptically) polarizing plate can be produced. The opticalcompensatory sheet is preferably placed so that the slow axis of thesheet may be oriented in average at an angle of 3° or less to thetransmission axis of the polarizing membrane. The angle is morepreferably 2° or less, most preferably 1° or less.

In the case where the polarizing membrane and the optical compensatorysheet comprising liquid crystal molecules are laminated to prepare anelliptically polarizing plate, the compensatory sheet can serve as oneof the transparent protective films. The thus-prepared ellipticallypolarizing plate has a layered structure in which a transparentprotective film, the polarizing membrane, a transparent support, and anoptically anisotropic layer comprising liquid crystal molecules arelayered in this order. The support and the anisotropic layer constitutethe optical compensatory sheet. Since a liquid crystal display isgenerally wanted to be as both thin and light-weight as possible, it ispreferred to reduce the number of members constituting the display. Formthis viewpoint, the above polarizing plate in which one member plays tworoles (namely, the compensatory sheet not only optically compensates thedisplayed image but also functions as a protective film) is preferablyused in a liquid crystal display. In addition, the liquid crystaldisplay consisting of reduced members can be produced through reducedsteps for laminating. Accordingly, troubles in the production steps canbe reduced. Japanese Patent Provisional Publication Nos. 7(1995)-191217,8(1996)-21996 and 8(1996)-94838 describe the unified ellipticallypolarizing plate in which one film functions not only as one of theprotective films protecting the polarizing membrane but also as thesupport of the optical compensatory sheet comprising liquid crystalmolecules.

A TFT liquid crystal display of TN mode is often equipped with theaforementioned unified elliptically polarizing plate, in which thetransparent support of the optical compensatory sheet comprising liquidcrystal molecules serves as one of the protective films of thepolarizing plate. That liquid crystal display thermally deforms, and isliable to give an image with leaked light. The thermal deformationchanges optical characters of the optical compensatory sheet, andconsequently causes the light-leakage. Particularly, a film of polymerhaving hydroxyl groups (such as a cellulose ester film) is largelyaffected by the environmental conditions. For reducing the light-leakagecaused by the thermal deformation, the inventors have found that it iseffective to lower the photoelasticity of the optical compensatory sheetand particularly to thin down the cellulose ester film.

However, the inventors have also found that it is difficult to handlethe thin cellulose ester film when the gelatin-undercoating layer isprovided through a coating procedure.

If the optical compensatory sheet is produced according to the processof the invention, it is not necessary to provide thegelatin-undercoating layer. Accordingly, the process of the invention isalso effective in producing the thin optical compensatory sheet havingexcellent planeness.

(Circularly Polarizing Plate)

A circularly polarizing plate can be produced if the opticalcompensatory sheet is used as a λ/4 plate. In that case, the opticalcompensatory sheet is laminated on the polarizing membrane so that theslow axis in the plane of the sheet may be oriented essentially at theangle of 45° to the polarizing axis of the membrane. The term“essentially at the angle of 45°” means the angle is in the range of 40°to 50°. The angle is preferably in the range of 41° to 49°, morepreferably in the range of 42° to 48°.

(Liquid Crystal Display)

The optical compensatory sheet of the invention or the polarizing platecomprising the sheet of the invention is advantageously used in a liquidcrystal display, especially in a liquid crystal display of transmissiontype.

A liquid crystal display of transmission type comprises a pair ofpolarizing plates and a liquid crystal cell placed between them. Theliquid crystal cell comprises a pair of electrode substrates and liquidcrystal molecules provided between them.

The optical compensatory sheet of the invention is placed between thecell and one or each of the polarizing plates.

The polarizing plate of the invention is used as one or each of the pairof polarizing plates. In that case, the plate of the invention is placedso that the compensatory sheet of the plate may face to the liquidcrystal cell.

The optical compensatory sheet or the polarizing plate according to theinvention is particularly advantageously used in a liquid crystaldisplay having a liquid crystal cell of TN mode, VA mode and OCB mode.

In a liquid crystal cell of TN mode, rod-like liquid crystal moleculesare essentially horizontally aligned while voltage is not applied, andoriented in a twisted alignment with a twisted angle of 60 to 120°. Theliquid crystal cell of TN mode is widely used in color TFT liquidcrystal displays, and hence is described in many publications.

In a liquid crystal cell of VA mode, rod-like liquid crystal moleculesare essentially vertically aligned while voltage is not applied.

The liquid crystal cell of VA mode include some types: (1) a liquidcrystal cell of VA mode in a narrow sense (described in Japanese PatentProvisional Publication No. 2(1990)-176625), in which rod-like liquidcrystal molecules are essentially vertically aligned while voltage isnot applied, and the molecules are essentially horizontally alignedwhile voltage is applied; (2) a liquid crystal cell of MVA mode(described in SID97, Digest of tech. Papers, 28(1997), 845), in whichthe VA mode is modified to be multi-domain type so as to enlarge theviewing angle; (3) a liquid crystal cell of n-ASM mode (described inAbstracts of Japanese Forum of Liquid Crystal (written in Japanese),(1998), pp. 58 to 59), in which rod-like liquid crystal molecules areessentially vertically aligned while voltage is not applied, and themolecules are essentially oriented in twisted multi-domain alignmentwhile voltage is applied; and (4) a cell of SURVAIVAL mode (presented inLCD International '98).

The liquid crystal cell of OCB mode is a liquid crystal cell of bendalignment mode in which rod-like liquid crystal molecules in upper partand ones in lower part are essentially reversely (symmetrically)aligned. A liquid crystal display having the liquid crystal cell of bendalignment mode is disclosed in U.S. Pat. Nos. 4,583,825 and 5,410,422.Since rod-like liquid crystal molecules in upper part and ones in lowerpart are symmetrically aligned, the liquid crystal cell of bendalignment mode has self-optical compensatory function. Therefore, thismode is referred to as OCB (optically compensatory bend) mode. Theliquid crystal display of bend alignment mode has an advantage ofresponding rapidly since rod-like liquid crystal molecules in upper partand ones in lower part are symmetrically aligned.

(Liquid Crystal Display of Reflection Type)

The optical compensatory sheet of the invention is also advantageouslyused in a liquid crystal display of reflection type. In that case, thecompensatory sheet is preferably used as a λ/4 plate in a liquid crystaldisplay explained below as an example. The circularly polarizing plateaccording to the invention may be used as a λ/4 plate or a polarizingmembrane.

The liquid crystal display of reflection type comprises a lowersubstrate, a reflective electrode, a lower orientation layer, a liquidcrystal layer, an upper orientation layer, a transparent electrode, anupper substrate, a λ/4 plate, and a polarizing membrane, layered in thisorder.

A combination of the lower substrate and the reflective electrodeconstitutes a reflection board. A combination of the lower orientationlayer to the upper orientation layer constitutes a liquid crystal cell.The λ/4 plate may be placed at any position between the reflection boardand the polarizing membrane.

For displaying a color image, a color filter layer is additionallyprovided. The color filter is preferably placed between the reflectiveelectrode and the lower orientation layer, or between the upperorientation layer and the transparent electrode.

In place of the reflective electrode, another transparent electrode maybe used in combination with a reflection board. The reflection board ispreferably a metal board. If the reflection board has a smooth surface,rays parallel to the normal of the surface are often predominantlyreflected to give a small viewing angle. Therefore, the surface of thereflection board is preferably made rugged (as described in JapanesePatent No. 275,620). Otherwise, a light-diffusing film may be providedon one surface (cell side or air side) of the polarizing membrane.

The liquid crystal cell is preferably TN (twisted nematic) mode, STN(supper twisted nematic) mode, or HAN (hybrid aligned nematic) mode.

The liquid crystal cell of TN mode has a twist angle preferably in therange of 40 to 100°, more preferably in the range of 50 to 90°, mostpreferably in the range of 60 to 80°. The product (Δn·d) of refractiveanisotropy (Δn) and thickness (d) of the liquid crystal layer ispreferably in the range of 0.1 to 0.5 μm, more preferably in the rangeof 0.2 to 0.4 μm.

The liquid crystal cell of STN mode has a twist angle preferably in therange of 180 to 360°, more preferably in the range of 220 to 270°. Theproduct (Δn·d) of refractive anisotropy (Δn) and thickness (d) of theliquid crystal layer is preferably in the range of 0.3 to 1.2 μm, morepreferably in the range of 0.5 to 1.0 μm.

In the liquid crystal cell of HAN mode, it is preferred that liquidcrystal molecules be essentially vertically aligned on one substrate andthat the pre-tilt angle on the other substrate be in the range of 0 to45°. The product (Δn·d) of refractive anisotropy (Δn) and thickness (d)of the liquid crystal layer is preferably in the range of 0.1 to 1.0 μm,more preferably in the range of 0.3 to 0.8 μm. The substrate on whichthe liquid crystal molecules are vertically aligned may be on thetransparent electrode side or on the reflection board side.

The liquid crystal display of reflection type may be a display ofguest-host type.

The guest-host display of reflection type comprises a lower substrate,an organic membrane insulating the layers, a metal reflection board, aλ/4 plate, a lower transparent electrode, a lower orientation layer, aliquid crystal layer, an upper orientation layer, an upper transparentelectrode, a light-diffusing film, an upper substrate, and ananti-reflection film, layered in this order. A TFT is provided betweenthe lower substrate and the organic membrane insulating the layers.

In place of providing the light-diffusing film, the surface of thereflection board may be made rugged to give the light-diffusing functionto the board. The anti-reflection film preferably has an anti-glarefunction as well as the anti-reflection function.

EXAMPLE 1

(Preparation of Cellulose Ester Film)

The following components were placed in a mixing tank, and then heatedand stirred to dissolve. Thus, a cellulose acetate solution wasprepared.

Components of cellulose acetate solution Cellulose acetate (acetic acidcontent: 60.9%) 100 weight parts Triphenyl phosphate 7.8 weight partsBiphenyldiphenyl phosphate 3.9 weight parts Methylene chloride 300weight parts Methanol 54 weight parts 1-Butanol 11 weight parts

In another mixing tank, the following components were placed, heated andstirred to dissolve. Thus, a retardation-increasing agent solution wasprepared.

Components of retardation-increasing agent solution2-Hydroxy-4-benzyloxybenzophenone 12 weight parts2,4-Benzyloxybenzophenone  4 weight parts Methylene chloride 80 weightparts Methanol 20 weight parts

The prepared retardation-increasing agent solution in the amount of 22weight parts was added to 474 weight parts of the cellulose acetatesolution, and stirred well to mix. The thus-prepared dope contained 3weight parts of the retardation-increasing agent based on 100 weightparts of cellulose acetate.

The dope was cast from a nozzle onto a drum cooled at 0° C. The formedfilm was peeled when the solvent content reached 70 wt. %, and bothsides of the film was fixed with a pin tenter. While the film was set upso that the stretching ratio might be kept 3% in the lateral direction(perpendicular to the machine), the film was dried until the solventcontent reached 3 to 5 wt. %. The film was then transferred and furtherdried in a heating apparatus equipped with many rollers. The stretchingratio along the machine was essentially 0% at a temperature higher than120° C., which is the glass transition temperature. In order to stretchthe film along the machine by 4% when the film was peeled, thestretching ratio in the direction perpendicular to the machine was 0.75times as much as the total stretching ratio along the machine. Thus, acellulose acetate film having 107 μm thickness (CA-1) was produced.

The retardation of the produced film was measured to find that the Rthand Re were 80 nm and 11 nm, respectively

(Saponification Treatment and Formation of Orientation Layer)

The cellulose acetate film (CA-1) was coated with 1.5 N KOH-isopropylalcohol solution in the amount of 25 ml/m², and dried at 25° C. for 5seconds. The coated surface of the film was then washed with flowingwater for 10 seconds, and blown with air at 25° C. to dry.

On the thus-treated surface, the following coating solution was thenapplied in the amount of 28 ml/m² by means of a wire bar coater of #16.The applied solution was dried with hot air at 60° C. for 60 seconds,and then further dried with hot air at 90° C. for 150 seconds.

The formed layer was subjected to the rubbing treatment in which therubbing direction was parallel to the longitudinal direction of the filmCA-1.

Coating solution for orientation layer The following denatured polyvinylalcohol 20 weight parts Water 360 weight parts Methanol 120 weight partsGlutaric aldehyde (cross-linking agent) 0.5 weight part

(Formation of Optically Anisotropic Layer)

The following discotic liquid crystal coating solution was applied bymeans of a wire bar coater of #4, and heated in a thermostat at 125° C.for 3 minutes to align the discotic liquid crystal molecules. Thethus-treated surface was then irradiated with ultraviolet rays emittedfrom a high-pressure mercury lamp at the exposure energy of 500 mJ/cm²,and then cooled to room temperature. Thus, an optical compensatory sheetKS-1 was produced.

Discotic liquid crystal coating solution The following discotic liquidcrystal DLC-A 9.1 weight parts Ethylene oxide denatured trimethylolpropane triacrylate 0.9 weight part (V#360, Osaka Organic Chemicals Col,Ltd.) Cellulose acetate butyrate (CAB-531-0.2, Eastman 0.2 weight partChemical) Cellulose acetate butyrate (CAB-531-1, Eastman Chemical) 0.05weight part Photopolymerization initiator (Irgacure 907, Ciba-Geigy) 3.0weight parts Sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) 0.1weight part Methyl ethyl ketone 25.9 weight parts

The formed optically anisotropic layer had the thickness of 1.8 μm. Theretardation of the optical compensatory sheet KS-1 was measured alongthe rubbing direction of the orientation layer, and thereby it was foundthat the average inclined angle of the optical axis was 18.0° and thatthe retardation values Rth and Re were 160 nm and 33 nm, respectively.Further, the optical compensatory sheet KS-1 was sandwiched between apair of polarizing plates in cross-Nicol arrangement, and it wasobserved whether striped unevenness occurred or not. The results are setforth in Table 1.

The optically anisotropic layer-side surface of the compensatory sheetKS-1 was laminated on a glass plate with an acrylic adhesive, and leftat 90° C. for 20 hours. The acrylic adhesive was the same as that usedfor assembling the liquid crystal display in the following examples, andthe glass plate was the same as that used in the liquid crystal cell inthe following examples. The compensatory sheet was then verticallypeeled from the glass plate, and the bared surface of the plate wasobserved to evaluate how much amount of the optically anisotropic layerof the compensatory sheet remained and thereby to estimate the adhesion.On the basis of the observation, the adhesion was classified into fivegrades of 0 (much amount of the anisotropic layer remained) to 5 (theanisotropic layer did not remained at all). The results are set forth inTable 1.

EXAMPLE 2

(Preparation of Cellulose Ester Film)

A three-layered casting die was used. The dope for inner layer was thecellulose acetate dope prepared in Example 1, and that for outer layerswas a diluted dope prepared in the same manner as that in Example 1except that the amount of the solvent was increased by 10%. The dopeswere simultaneously cast onto a metal support. The formed film waspeeled off, and dried to prepare a three-layered cellulose acetate film(thickness of inner layer: thickness of each outer layer=8:1). The filmwas stepwise dried at 70° C. for 3 minutes and at 130° C. for 5 minutes,and then peeled from the support. The peeled film was then further driedat 160° C. for 30 minutes to evaporate the solvent. Thus, a celluloseacetate film (CA-2) was prepared.

The retardation of the produced film was measured to find that the Rthand Re were 80 nm and 11 nm, respectively

(Saponification Treatment and Formation of Orientation Layer)

The cellulose acetate film (CA-2) was saponified and an orientationlayer was provided in the same manner as in Example 1. The orientationlayer was subjected to the rubbing treatment in which the rubbingdirection was parallel to the longitudinal direction of the film CA-2.

(Formation of Optically Anisotropic Layer)

An optically anisotropic layer was formed on the orientation layer ofthe cellulose acetate film CA-2 in the same manner as in Example 1, toproduce an optical compensatory sheet KS-2.

The formed optically anisotropic layer had the thickness of 1.8 μm. Theretardation of the optical compensatory sheet KS-2 was measured alongthe rubbing direction of the orientation layer, and thereby it was foundthat the average inclined angle of the optical axis was 18.0° and thatthe retardation values Rth and Re were 160 nm and 33 nm, respectively.Further, the optical compensatory sheet KS-2 was sandwiched between apair of polarizing plates in cross-Nicol arrangement, and it wasobserved whether striped unevenness occurred or not. The adhesion wasalso evaluated in the same manner as in Example 1. The results are setforth in Table 1.

EXAMPLE 3

(Preparation of Cellulose Ester Film)

The cellulose triacetate solution consisting of the following componentswere prepared. The solvents shown below were beforehand mixed, and thencellulose triacetate powder (mean particle size: 2 mm) was graduallyadded to the mixed solvent while stirred. The mixture was left at roomtemperature (25° C.) for 3 hours.

Components of cellulose acetate solution Cellulose acetate (acetic acidcontent: 60.9%)  100 weight parts Triphenyl phosphate  7.8 weight partsBiphenyldiphenyl phosphate  3.9 weight parts2-Hydroxy-4-benzyloxybenzophenone 2.25 weight parts2,4-Benzyloxybenzophenone 0.75 weight part Methyl acetate  282 weightparts Cyclopentanone  118 weight parts Methanol   29 weight partsEthanol   29 weight parts

The prepared dope was cast on a drum cooled at 0° C. The formed film waspeeled when the solvent content reached 70 wt. %, and both sides of thefilm was fixed with a pin tenter. While held so that the stretchingratio might be kept 3% in the lateral direction (perpendicular to themachine), the film was dried until the solvent content reached 3 to 5wt. %. The film was then transferred and further dried in a heatingapparatus equipped with many rollers. The stretching ratio along themachine was essentially 0% at a temperature higher than 120° C., whichis the glass transition temperature. In order to stretch the film alongthe machine by 4% when the film was peeled, the stretching ratio in thedirection perpendicular to the machine was 0.75 times as much as thetotal stretching ratio along the machine. Thus, a cellulose acetate filmhaving 107 μm thickness (CA-3) was produced.

The retardation of the produced film was measured to find that the Rthand Re were 80 nm and 11 nm, respectively

(Saponification Treatment and Formation of Orientation Layer)

The cellulose acetate film (CA-3) was saponified and an orientationlayer was provided in the same manner as in Example 1. The orientationlayer was subjected to the rubbing treatment in which the rubbingdirection was parallel to the longitudinal direction of the film CA-3.

(Formation of Optically Anisotropic Layer)

An optically anisotropic layer was formed on the orientation layer ofthe cellulose acetate film CA-3 in the same manner as in Example 1, toproduce an optical compensatory sheet KS-3.

The formed optically anisotropic layer had the thickness of 1.8 μm. Theretardation of the optical compensatory sheet KS-3 was measured alongthe rubbing direction of the orientation layer, and thereby it was foundthat the average inclined angle of the optical axis was 18.0° and thatthe retardation values Rth and Re were 160 nm and 33 nm, respectively.Further, the optical compensatory sheet KS-3 was sandwiched between apair of polarizing plates in cross-Nicol arrangement, and it wasobserved whether striped unevenness occurred or not. The adhesion wasalso evaluated in the same manner as in Example 1. The results are setforth in Table 1.

COMPARISON EXAMPLE 1

(Preparation of Cellulose Ester Film)

On the cellulose acetate film CA-1 prepared in Example 1, the followingcoating solution for gelatin-undercoating layer was applied in theamount of 28 ml/m². The applied solution was then dried to form agelatin-undercoating layer. Thus, a cellulose acetate film CA-4 wasprepared.

Coating solution for gelatin-undercoating layer Gelatin 5.42 weightparts Formaldehyde 1.39 weight parts Salicylic acid  1.6 weight partsAcetone  391 weight parts Methanol  158 weight parts Methylene chloride 406 weight parts Water   12 weight parts(Formation of Orientation Layer)

On the cellulose acetate film (CA-4), the coating solution fororientation layer used in Example 1 was applied in the amount of 28ml/m² by means of a wire bar coater of #16. The applied solution wasdried with hot air at 60° C. for 60 seconds, and then further dried withhot air at 90° C. for 150 seconds.

The formed layer was subjected to the rubbing treatment in which therubbing direction was parallel to the longitudinal direction of the filmCA-4.

(Formation of Optically Anisotropic Layer)

An optically anisotropic layer was formed on the orientation layer ofthe cellulose acetate film CA-4 in the same manner as in Example 1, toproduce an optical compensatory sheet KS-4.

The formed optically anisotropic layer had the thickness of 1.8 μm. Theretardation of the optical compensatory sheet KS-4 was measured alongthe rubbing direction of the orientation layer, and thereby it was foundthat the average inclined angle of the optical axis was 18.0° and thatthe retardation values Rth and Re were 160 nm and 33 nm, respectively.Further, the optical compensatory sheet KS-4 was sandwiched between apair of polarizing plates in cross-Nicol arrangement, and it wasobserved whether striped unevenness occurred or not. The adhesion wasalso evaluated in the same manner as in Example 1. The results are setforth in Table 1.

TABLE 1 Film Striped unevenness* Adhesion Example 1 KS-1 B 5 Example 2KS-2 A 5 Example 3 KS-3 B 5 Comp. Ex. 1 KS-4 C 5 (Remarks) *Grades ofstriped unevenness: A: not observed (if ten persons observed, none ofthem can notice the unevenness),

EXAMPLE 4

(Preparation of Polarizing Plate)

The optical compensatory sheet KS-1 prepared in Example 1 was immersedin 1.5 N NaOH aqueous solution (55° C.) for 2 minutes, neutralized with0.5 N sulfuric acid, washed with flowing water, and dried.

On the cellulose acetate film (CA-1)-side surface of the compensatorysheet KS-1, a polarizing membrane (stretched polyvinyl alcohol filmadsorbing iodine) was laminated with a polyvinyl alcohol adhesive.

On the opposite surface of the compensatory sheet KS-1, a saponifiedcommercially available cellulose acetate film (Fujitac TD80UF, FujiPhoto Film Co., Ltd.) was laminated with the polyvinyl alcohol adhesive.The polarizing membrane was placed so that the transmission axis of themembrane might be perpendicular to the slow axis of the compensatorysheet KS-1. Thus, a polarizing plate P-1 was prepared.

EXAMPLE 5

(Preparation of Polarizing Plate)

The procedure of Example 4 was repeated except that the opticalcompensatory sheet KS-2 prepared in Example 2 was used, to prepare apolarizing plate P-2.

EXAMPLE 6

(Preparation of Polarizing Plate)

The procedure of Example 4 was repeated except that the opticalcompensatory sheet KS-3 prepared in Example 3 was used, to prepare apolarizing plate P-3.

COMPARISON EXAMPLE 2

(Preparation of Polarizing Plate)

The procedure of Example 4 was repeated except that the opticalcompensatory sheet KS-4 prepared in Comparison Example 1 was used, toprepare a polarizing plate P-4.

EXAMPLE 7

A pair of polarizing plates was removed from a commercially availableliquid crystal display (6E-A3, Sharp Corporation), which had a liquidcrystal cell of TN mode. In place of the removed members, the polarizingplate P-1 prepared in Example 4 was laminated on each side (each of thebacklight side and the observer side) of the cell with an adhesive sothat the optical compensatory sheet KS-1 might be on the liquid crystalcell side. The polarizing plates were arranged so that the transmissionaxis of the plate on the observer side might be perpendicular to that ofthe plate on the backlight side.

The viewing angle of the prepared liquid crystal display was measured bymeans of a measuring apparatus (EZ-Contrast 160D, ELDIM) when each ofeight tones of black (L1) to white (L8) was displayed. The viewing anglewas represented by the angle range giving a contrast ratio of 10 or morewithout reversing black tones. Further, it was confirmed by the eyeswhether unevenness of displaying was observed or not when a dark imagewas displayed. The results are set forth in Table 2.

EXAMPLE 8

The procedure of Example 7 was repeated except that the polarizing plate(P-2) prepared in Example 5 was used, to prepare a liquid crystaldisplay.

The viewing angle of the prepared display was measured in the samemanner as in Example 7. Further, it was confirmed by the eyes whetherunevenness of displaying was observed or not when a dark image wasdisplayed. The results are set forth in Table 2.

EXAMPLE 9

The procedure of Example 7 was repeated except that the polarizing plateP-3 prepared in Example 6 was used, to prepare a liquid crystal display.

The viewing angle of the prepared display was measured in the samemanner as in Example 7. Further, it was confirmed by the eyes whetherunevenness of displaying was observed or not when a dark image wasdisplayed. The results are set forth in Table 2.

COMPARISON EXAMPLE 3

The procedure of Example 7 was repeated except that the polarizing plateP-4 prepared in Comparison Example 2 was used, to prepare a liquidcrystal display.

The viewing angle of the prepared display was measured in the samemanner as in Example 7. Further, it was confirmed by the eyes whetherunevenness of displaying was observed or not when a dark image wasdisplayed. The results are set forth in Table 2.

TABLE 2 Liquid crystal Viewing angle Uneven- display Upward DownwardLeft-rightward ness* Example 7 65° 35° 140° B Example 8 65° 35° 140° AExample 9 65° 35° 140° B Comp. Ex. 3 65° 35° 140° C (Remarks) *Grades ofunevenness: A: not observed (if ten persons observed, none of them cannotice the unevenness), B: slightly observed (if ten persons observed,one to five of them can notice the unevenness), and C: considerablyobserved (if ten persons observed, six or more of them can notice theunevenness).

EXAMPLE 10

(Preparation of Optical Compensatory Sheet)

The following components were placed in a mixing tank, and then heatedand stirred to dissolve. Thus, a cellulose acetate solution wasprepared.

Components of cellulose acetate solution Cellulose acetate (acetic acidcontent: 60.9%)  100 weight parts Triphenyl phosphate (plasticizer)  7.8weight parts Biphenyldiphenyl phosphate (plasticizer)  3.9 weight partsMethylene chloride (first solvent)  336 weight parts Methanol (secondsolvent)   29 weight parts

In another mixing tank, 16 weight parts of the followingretardation-increasing agent, 80 weight parts of methylene chloride and20 weight parts of methanol were placed, heated and stirred to dissolve.Thus, a retardation-increasing agent solution was prepared.

The prepared cellulose acetate solution and the retardation-increasingagent solution were mixed in amounts of 474 weight parts and 21 weightparts, respectively, and stirred well to prepare a dope. The content ofthe retardation-increasing agent in the dope was 2.8 weight parts basedon 100 weight parts of cellulose acetate.

The prepared dope was cast onto a film-forming band. When the remainingsolvent reached 50 wt. %, the formed film was peeled from the band anddried. When the remaining solvent reached 40 wt. %, the film waslaterally stretched at 130° C. in the extension ratio of 20% by means ofa tenter. The film was held at 130° C. for 30 seconds with the stretchedwidth maintained, and then released from the clips. Thus, a celluloseacetate film CA-5 (thickness: 95 μm) was prepared.

The retardation of the produced film was measured to find that the Rthand Re were 110 nm and 20 nm, respectively

(Saponification Treatment and Formation of Orientation Layer)

The cellulose acetate film (CA-5) was coated with 1.5 N KOH-isopropylalcohol solution in the amount of 25 ml/m², and dried at 25° C. for 5seconds. The coated surface of the film was then washed with flowingwater for 10 seconds, and blown with air at 25° C. to dry.

On the thus-treated surface, the following coating solution was thenapplied in the amount of 21 ml/m² by means of a wire bar coater of #12.The applied solution was dried with hot air at 120° C. for 120 seconds.

The formed layer was subjected to the rubbing treatment in which therubbing direction was parallel to the longitudinal direction of the filmCA-5.

Coating solution for orientation layer The following polymer material 4weight parts Water 280 weight parts Methanol 120 weight parts Triethylamine 5.6 weight parts

(Formation of Optically Anisotropic Layer)

The following discotic liquid crystal coating solution was applied onthe formed orientation layer by means of a wire bar coater of #3, andheated in a thermostat at 90° C. for 2 minutes to align the discoticliquid crystal molecules. The thus-treated surface was then irradiatedwith ultraviolet rays emitted from a high-pressure mercury lamp at theexposure energy of 250 mJ/cm², and then cooled to room temperature.Thus, an optical compensatory sheet KS-5 was produced.

Discotic liquid crystal coating solution The following liquid crystalLC-A 80.0 weight parts The following horizontally aligning agent 0.24weight part Cellulose acetate butyrate (CAB-531-0.2, Eastman 0.16 weightpart Chemical) Photopolymerization initiator (Irgacure 907, Ciba- 2.4weight parts Geigy) Sensitizer (Kayacure DETX, Nippon Kayaku Co., 0.8weight part Ltd.) Methyl ethyl ketone 1095.8 weight parts

R: —O—(CH₂)₄—O—CO—CH═CH₂

The formed optically anisotropic layer had the thickness of 0.4 μm. Theretardation of the optical compensatory sheet KS-5 was measured alongthe rubbing direction of the orientation layer, and thereby it was foundthat the retardation value Re was 45 nm and that the rod-like liquidcrystal molecules were horizontally aligned. Further, the opticalcompensatory sheet KS-5 was sandwiched between a pair of polarizingplates in cross-Nicol arrangement, and it was observed whether stripedunevenness occurred or not. The adhesion was also evaluated in the samemanner as in Example 1. The results are set forth in Table 3.

COMPARISON EXAMPLE 4

(Preparation of Cellulose Ester Film)

On the cellulose acetate film CA-5 prepared in Example 10, agelatin-undercoating layer was formed in the same manner as inComparison Example 1 to prepare a cellulose acetate film CA-6.

(Saponification Treatment and Formation of Orientation layer)

On the gelatin-undercoating layer of the cellulose acetate film CA-6, anorientation layer was formed in the same manner as in Example 10. Theformed orientation layer was then subjected to the rubbing treatment inwhich the rubbing direction was parallel to the longitudinal directionof the film CA-6.

(Formation of Optically Anisotropic Layer)

An optically anisotropic layer was formed on the orientation layer ofthe cellulose acetate film CA-6 in the same manner as in Example 10, toproduce an optical compensatory sheet KS-6.

The formed optically anisotropic layer had the thickness of 0.4 μm. Theretardation of the optical compensatory sheet KS-6 was measured alongthe rubbing direction of the orientation layer, and thereby it was foundthat the retardation value Re was 45 nm and that the rod-like liquidcrystal molecules were horizontally aligned. Further, the opticalcompensatory sheet KS-6 was sandwiched between a pair of polarizingplates in cross-Nicol arrangement, and it was observed whether stripedunevenness occurred or not. The adhesion was also evaluated in the samemanner as in Example 1. The results are set forth in Table 3.

EXAMPLE 11

(Formation of Optically Anisotropic Layer)

The orientation layer formed on the saponified surface of the celluloseacetate film (CA-1) prepared in Example 1 was subjected to the rubbingtreatment in which the rubbing direction was at 45° to the slow axis ofthe film.

The discotic liquid crystal coating solution used in Example 1 wasapplied on the formed orientation layer by means of a wire bar coater of#3, and heated in a thermostat at 125° C. for 3 minutes to align thediscotic liquid crystal molecules. The thus-treated surface was thenirradiated with ultraviolet rays emitted from a high-pressure mercurylamp at the exposure energy of 500 mJ/cm², and then cooled to roomtemperature. Thus, an optical compensatory sheet KS-7 was produced.

The formed optically anisotropic layer had the thickness of 1.8 μm. Theretardation of the optical compensatory sheet KS-7 was measured alongthe rubbing direction of the orientation layer, and thereby it was foundthat the average inclined angle of the optical axis was 18.0° and thatthe retardation values Rth and Re were 160 nm and 38 nm, respectively.Further, the optical compensatory sheet KS-7 was sandwiched between apair of polarizing plates in cross-Nicol arrangement, and it wasobserved whether striped unevenness occurred or not. The adhesion wasalso evaluated in the same manner as in Example 1. The results are setforth in Table 3.

COMPARISON EXAMPLE 5

(Formation of Optically Anisotropic Layer)

The orientation layer formed on the gelatin-undercoating layer of thecellulose acetate film (CA-4) prepared in Comparison Example 1 wassubjected to the rubbing treatment in which the rubbing direction was at45° to the slow axis of the film.

The optically anisotropic layer was formed in the same manner as inExample 11 to produce an optical compensatory sheet KS-8.

The formed optically anisotropic layer had the thickness of 0.4 μm. Theretardation of the optical compensatory sheet KS-8 was measured alongthe rubbing direction of the orientation layer, and thereby it was foundthat the retardation value Re was 45 nm and that the rod-like liquidcrystal molecules were horizontally aligned. Further, the opticalcompensatory sheet KS-8 was sandwiched between a pair of polarizingplates in cross-Nicol arrangement, and it was observed whether stripedunevenness occurred or not. The adhesion was also evaluated in the samemanner as in Example 1. The results are set forth in Table 3.

TABLE 3 Film Striped unevenness* Adhesion Example 10 KS-5 B 5 Comp.Example 4 KS-6 C 5 Example 11 KS-7 B 5 Comp. Example 5 KS-8 C 5(Remarks) *Grades of striped unevenness: B: slightly observed (if tenpersons observed, one to five of them can notice the unevenness), and C:considerably observed (if ten persons observed, six or more of them cannotice the unevenness).

EXAMPLE 12

(Preparation of Polarizing Plate)

The optical compensatory sheets KS-5 and KS-7 prepared in Examples 10and 11, respectively, were immersed in 1.5 N NaOH aqueous solution (55°C.) for 2 minutes, neutralized with 0.5 N sulfuric acid, washed withflowing water, and dried.

On the cellulose acetate film (CA-5)-side surface of the compensatorysheet KS-5, a polarizing membrane (stretched polyvinyl alcohol filmadsorbing iodine) was laminated with a polyvinyl alcohol adhesive.Further, the optically anisotropic layer-side surface of the sheet KS-5and the cellulose acetate film (CA-1)-side surface of the compensatorysheet KS-7 were laminated with a polyvinyl alcohol adhesive.

On the opposite surface of the polarizing membrane, a saponifiedcommercially available cellulose acetate film (Fujitac TD80UF, FujiPhoto Film Co., Ltd.) was laminated with the polyvinyl alcohol adhesive.The polarizing membrane was placed so that the transmission axis of themembrane might be parallel to the slow axis of the compensatory sheetKS-5 and might be at 45° to the slow axis of the compensatory sheetKS-7. Thus, a polarizing plate P-5 was prepared.

COMPARISON EXAMPLE 6

(Preparation of Polarizing Plate)

The procedure of Example 12 was repeated except that the opticalcompensatory sheets KS-6 and KS-8 prepared in Comparison Examples 4 and5, respectively, were used, to prepare a polarizing plate P-6.

EXAMPLE 13

On a glass plate having an ITO electrode, an orientation layer ofpolyimide was provided and subjected to a rubbing treatment. Thisprocedure was repeated to prepare two substrates, and the substrateswere arranged face-to-face so that the rubbing directions might beparallel and that the gap might be 6 μm. Between them, a liquid crystalhaving Δn of 0.1396 (ZLI1132, Merck & Co., Inc.) was introduced toprepare a liquid crystal cell of bend alignment.

The polarizing plate P-5 prepared in Example 12 was laminated on eachsurface of the liquid crystal cell, so that the cell was between theplates. The plates were arranged so that the optically anisotropic layerin each plate might face to the cell substrate and that the rubbingdirections of the cell and the optically anisotropic layer might beanti-parallel.

The viewing angle of the prepared liquid crystal display was measured bymeans of a measuring apparatus (EZ-Contrast 160D, ELDIM) when each ofeight tones of black (L1) to white (L8) was displayed. The viewing anglewas represented by the angle range giving a contrast ratio of 10 or morewithout reversing black tones. Further, it was confirmed by the eyeswhether unevenness of displaying was observed or not when a dark imagewas displayed. The results are set forth in Table 4.

COMPARISON EXAMPLE 7

The procedure of-Example 13 was repeated except that the polarizingplate P-6 prepared in Comparison Example 6 was used, to prepare a liquidcrystal display.

The viewing angle of the prepared display was measured in the samemanner as in Example 13. Further, it was confirmed by the eyes whetherunevenness of displaying was observed or not when a dark image wasdisplayed. The results are set forth in Table 4.

TABLE 4 Liquid crystal Viewing angle display Up-downward Left-rightwardUnevenness* Example 13 160° 160° B Comp. Example 7 160° 160° C (Remarks)*Grades of unevenness: B: slightly observed (if ten persons observed,one to five of them can notice the unevenness), and C: considerablyobserved (if ten persons observed, six or more of them can notice theunevenness).

EXAMPLE 14

(Preparation of Cellulose Ester Film)

The following components were placed in a mixing tank, and then heatedand stirred to dissolve. Thus, a cellulose acetate solution wasprepared.

Components of cellulose acetate solution Cellulose acetate (acetic acidcontent: 60.9%)  100 weight parts Triphenyl phosphate  7.8 weight partsBiphenyldiphenyl phosphate  3.9 weight parts Methylene chloride  300weight parts Methanol   54 weight parts 1-Butanol   11 weight parts

In another mixing tank, the following components were placed, heated andstirred to dissolve. Thus, a retardation-increasing agent solution wasprepared.

Components of retardation-increasing agent solution Theretardation-increasing agent used in Example 10 16 weight partsMethylene chloride 80 weight parts Methanol 20 weight parts

The prepared retardation-increasing agent solution in the amount of 21weight parts was added to 479 weight parts of the cellulose acetatesolution, and stirred well to mix. The thus-prepared dope contained 3weight parts of the retardation-increasing agent based on 100 weightparts of cellulose acetate.

The prepared dope was cast onto a film-forming band. The formed dopefilm had been dried on the band for 1 minute since the temperature ofthe film reached 40° C. After peeled from the band, the film was furtherdried to prepare a cellulose acetate film CA-9 (thickness: 40 μm), inwhich the solvent remained in the amount of 0.3 wt. %.

The retardation of the produced film CA-9 was measured to find that theRth and Re were 40 nm and 7 nm, respectively.

(Saponification Treatment and Formation of Orientation Layer)

The cellulose acetate film (CA-9) was saponified and an orientationlayer was provided in the same manner as in Example 1. The orientationlayer was subjected to the rubbing treatment in which the rubbingdirection was parallel to the longitudinal direction of the film CA-9.

(Formation of Optically Anisotropic Layer)

A solution in which the following liquid-crystalline polyester (EPE01)was dissolved in tetrachloroethane in the amount of 8 wt. % wasprepared. The solution was applied on the orientation layer of thecellulose acetate film CA-9 according to the spin-coating method. Afterthe solvent was removed, the film was heated at 190° C. for 20 minutesand then cooled with air to fix the alignment of the liquid-crystallinepolyester. Thus, an optical compensatory sheet KS-9 was produced.

(The subscript attached to each repeating unit represents the molarratio of each unit.)

The formed optically anisotropic layer had the thickness of 1.55 μm. Theretardation of the optical compensatory sheet KS-9 was measured alongthe rubbing direction of the orientation layer, and thereby it was foundthat the average inclined angle of the optical axis was 42° and that theretardation value Re was 43 nm.

Further, the optical compensatory sheet KS-9 was sandwiched between apair of polarizing plates in cross-Nicol arrangement, and it wasobserved whether striped unevenness occurred or not. The adhesion wasalso evaluated in the same manner as in Example 1. The results are setforth in Table 5.

COMPARISON EXAMPLE 8

(Preparation of Cellulose Ester Film)

On the cellulose acetate film CA-9 prepared in Example 13, agelatin-undercoating layer was formed in the same manner as inComparison Example 1 to prepare a cellulose acetate film CA-10.

(Formation of Orientation Layer)

On the gelatin-undercoating layer of the cellulose acetate film CA-10,an orientation layer was formed in the same manner as in Example 1. Theformed orientation layer was then subjected to the rubbing treatment inwhich the rubbing direction was parallel to the longitudinal directionof the film CA-10.

(Formation of Optically Anisotropic Layer)

An optically anisotropic layer was formed on the orientation layer ofthe cellulose acetate film CA-10 in the same manner as in Example 14, toproduce an optical compensatory sheet KS-10.

The formed optically anisotropic layer had the thickness of 1.55 μm. Theretardation of the optical compensatory sheet KS-10 was measured alongthe rubbing direction of the orientation layer, and thereby it was foundthat the average inclined angle of the optical axis was 42° and that theretardation value Re was 43 nm.

Further, the optical compensatory sheet KS-10 was sandwiched between apair of polarizing plates in cross-Nicol arrangement, and it wasobserved whether striped unevenness occurred or not. The adhesion wasalso evaluated in the same manner as in Example 1. The results are setforth in Table 5.

TABLE 5 Film Striped unevenness* Adhesion Example 14 KS-9 B 5 Comp.Example 8 KS-10 C 5 (Remarks) *Grades of striped unevenness: B: slightlyobserved (if ten persons observed, one to five of them can notice theunevenness), and C: considerably observed (if ten persons observed, sixor more of them can notice the unevenness).

EXAMPLE 15

(Preparation of Polarizing Plate)

The procedure of Example 4 was repeated except that the opticalcompensatory sheet KS-9 prepared in Example 14 was used, to prepare apolarizing plate P-7.

COMPARISON EXAMPLE 9

(Preparation of Polarizing Plate)

The procedure of Example 4 was repeated except that the opticalcompensatory sheet KS-10 prepared in Comparison Example 8 was used, toprepare a polarizing plate P-8.

EXAMPLE 16

The procedure of Example 7 was repeated except that the polarizing plateP-7 prepared in Example 15 was used, to prepare a liquid crystaldisplay.

The viewing angle of the prepared display was measured in the samemanner as in Example 7. Further, it was confirmed by the eyes whetherunevenness of displaying was observed or not when a dark image wasdisplayed. The results are set forth in Table 6.

COMPARISON EXAMPLE 10

The procedure of Example 7 was repeated except that the polarizing plateP-8 prepared in Comparison Example 9 was used, to prepare a liquidcrystal display.

The viewing angle of the prepared display was measured in the samemanner as in Example 7. Further, it was confirmed by the eyes whetherunevenness of displaying was observed or not when a dark image wasdisplayed. The results are set forth in Table 6.

TABLE 6 Liquid crystal Viewing angle Uneven- display Upward DownwardLeft-rightward ness* Example 16 45° 60° 140° B Comp. Ex. 10 45° 60° 140°C (Remarks) *Grades of unevenness: B: slightly observed (if ten personsobserved, one to five of them can notice the unevenness), and C:considerably observed (if ten persons observed, six or more of them cannotice the unevenness).

EXAMPLE 17

(Preparation of Cellulose Ester Film-1)

From the dope prepared in Example 1, a cellulose acetate film wasprepared according to each of the following processes (a) and (b).

(a) Single-Layered Film Formation (Preparation of Cellulose Acetate FilmCA-11)

The dope was cast from a nozzle onto a drum cooled at 0° C. The formedfilm was peeled when the solvent content reached 70 wt. %, and bothsides of the film was fixed ith a pin tenter. While held so that thestretching ratio might be kept 3% in the lateral direction(perpendicular to the machine), the film was dried until the solventcontent reached 3 to 5 wt. %. The film was then transferred and furtherdried in a heating apparatus equipped with many rollers. The stretchingratio along the machine was essentially 0% at a temperature higher than120° C., which is the glass transition temperature. In order to stretchthe film along the machine by 4% when the film was peeled, thestretching ratio in the direction perpendicular to the machine was 0.75times as much as the total stretching ratio along the machine. Thus, acellulose acetate film having 107 μm thickness (CA-11) was produced.

(b) Multi-Layered Film Formation (Preparation of Cellulose Acetate FilmCA-12)

A three-layered casting die was used. The dope for inner layer was thecellulose acetate dope prepared in Example 1, and that for outer layerswas a diluted dope prepared in the same manner as that in Example 1except that the amount of the solvent was increased by 10%. The dopeswere simultaneously cast from the die onto a metal support. The formedfilm was treated in the same manner as in the above film-formation (a),to prepare a cellulose acetate film having 107 μm thickness (CA-12).

From each prepared film, both side areas inner by 15 cm from the edgeswere trimmed. Further, knurls (height: 50 μm, width: 1 cm) were providednear the edges. Thus, a cellulose acetate film (width: 1.5 m, length:3,000 m) was prepared. The wastes of the film produced in the trimmingwere pulverized and mixed with virgin cellulose acetate to reuse. (Thecontent of the reused cellulose acetate was 30 wt. % based on the totalamount of cellulose acetate.)

(Preparation of Cellulose Ester Film-2: CA-13)

The dope prepared in Example 3 was cast from a nozzle onto a drum cooledat 0° C. The formed film was peeled when the solvent content reached 70wt. %, and both sides of the film was fixed with a pin tenter. Whileheld so that the stretching ratio might be kept 3% in the lateraldirection (perpendicular to the machine), the film was dried until thesolvent content reached 3 to 5 wt. %. The film was then transferred andfurther dried in a heating apparatus equipped with many rollers. Thestretching ratio along the machine was essentially 0% at a temperaturehigher than 120° C., which is the glass transition temperature. In orderto stretch the film along the machine by 4% when the film was peeled,the stretching ratio in the direction perpendicular to the machine was0.75 times as much as the total stretching ratio along the machine.Thus, a cellulose acetate film having 107 μm thickness (CA-13) wasproduced.

(Saponification Treatment)

One surface of each prepared film (CA-11 to CA-13) was coated with 1.5 NKOH aqueous solution (alkaline solution) in the amount of 25 ml/m², andheld at 25° C. for 5 seconds to saponify. The alkaline solution was thenwashed away with flowing water for 10 seconds, and the washed surfacewas blown with air at 25° C. to dry. The conditions of thesaponification treatment such as oxygen gas concentration in theatmosphere, solvent components of the KOH solution, and temperature ofthe flowing water (washing water) are set forth in Table 7. Thus,cellulose acetate films used for the below-described opticalcompensatory sheets 17-1 to 17-9 were prepared. The surface propertiesof each cellulose acetate film were measured, and the results are setforth in Table 7.

(Formation of Orientation Layer)

On the saponified surface of each prepared cellulose acetate film, anorientation layer was provided in the same manner as in Example 1.

(Formation of Optically Anisotropic Layer)

An optically anisotropic layer was formed on the orientation layer ofeach cellulose acetate film in the same manner as in Example 1, toproduce optical compensatory sheets 17-1 to 17-9.

Each formed optically anisotropic layer had the thickness of 1.8 μm. Theretardation of each optical compensatory sheet (17-1 to 17-9) wasmeasured along the rubbing direction of the orientation layer, andthereby it was found that the average inclined angles of the opticalaxes in the sheets were in the range of 17° to 19° and that theretardation values Rth and Re of the sheets were in the ranges of 150 to170 nm and 31 to 35 nm, respectively.

On the optically anisotropic layer of each compensatory sheet, a checkedpattern (consisting of five lateral lines and five vertical lines drawnat intervals of 5 mm) was carved with a razor. The depth of the notcheswas controlled not to cut the sheet but to reach the surface of thecellulose acetate film. Each optical compensatory sheet was thenlaminated on a glass plate with an acrylic adhesive so that theoptically anisotropic layer-side surface of each sheet might be incontact with the glass plate. The acrylic adhesive was the same as thatused for assembling the liquid crystal display in the followingexamples, and the glass plate was also the same as that used in theliquid crystal cell in the following examples. Each thus-prepared samplewas left at 90° C. for 20 hours. The compensatory sheet of each samplewas then vertically peeled from the glass plate, and the bared surfaceof the plate was observed to evaluate how much amount of the opticallyanisotropic layer of each compensatory sheet remained and thereby toestimate the adhesion. Since the surface of the compensatory sheet wascurved, this adhesion test is severer than that in Example 1 and hencethe endurance in sizing can be more suitably estimated. The test wascarried out under each condition of 25° C. (temperature), 10% RH(humidity) and 25° C. (temperature), 60% RH (humidity). Although thesheet is practically sized under the latter condition, the test underthe former condition was performed to estimate the endurance of thesheet under a severer condition. The adhesion was evaluated in terms ofthe percent ratio (%) of peeled area. The results are set forth in Table7.

(Preparation of Polarizing Plate)

All the optical compensatory sheets were immersed in 1.5 N NaOH aqueoussolution (55° C.) for 2 minutes, neutralized with 0.5 N sulfuric acid,washed with flowing water, and dried.

On the cellulose acetate film-side surface of each compensatory sheet, apolarizing membrane (stretched polyvinyl alcohol film adsorbing iodine)was laminated with a polyvinyl alcohol adhesive. The polarizing membranewas placed so that the transmission axis of the membrane might beperpendicular to the slow axis of the compensatory sheet.

On the opposite surface of each compensatory sheet, a saponifiedcommercially available cellulose acetate film (Fujitac TD80UF, FujiPhoto Film Co., Ltd.) was laminated with the polyvinyl alcohol adhesive.Thus, a polarizing plate comprising each optical compensatory sheet wasproduced.

(Preparation of Liquid Crystal Display)

A pair of polarizing plates was removed from a commercially availableliquid crystal display (6E-A3, Sharp Corporation), which had a liquidcrystal cell of TN mode. In place of the removed members, each preparedpolarizing plate was laminated on each side (each of the backlight sideand the observer side) of the cell with an adhesive so that the opticalcompensatory sheet might be on the liquid crystal cell side. Thepolarizing plates were arranged (in O mode) so that the transmissionaxis of the plate on the observer side might be perpendicular to that ofthe plate on the backlight side.

The viewing angle of the prepared liquid crystal display was measured bymeans of a measuring apparatus (EZ-Contrast 160D, ELDIM) when each ofeight tones of black (L1) to white (L8) was displayed. The viewing anglewas represented by the angle range giving a contrast ratio of 10 or morewithout reversing black tones. Further, it was confirmed by the eyes howmuch undesirable brilliant points were observed when a dark image wasdisplayed. Before the displays were prepared, each compensatory sheetwas sized under each condition of 25° C. (temperature), 10% RH(humidity) and 25° C. (temperature), 60% RH (humidity). Althoughpractically sized under the latter condition, the sheet was also sizedunder the former condition to estimate troubles under a severercondition.

Also before the displays were prepared, all the prepared polarizingplates were left at 80° C. for 30 days (test for shelf life in longterm). Independently, they were also left under a moderate condition,namely at 50° C. for 30 days. With each polarizing plate, the liquidcrystal display was prepared. While each prepared display was giving awhite image, it was observed by the eyes to confirm how much thedisplayed image was fogged. The fogs were evaluated in terms of thepercent ratio (%) of fogged area based on the whole area of thedisplayed image. The results are set forth in Table 7.

TABLE 7 Saponification condition Trans- Tempera- parent Exten- Oxygenture of sup- sion Solvent concen- washing port ratio (wt. %) trationwater 17-1 CA-11 1 IPA (100) 3% 60° 17-2 CA-11 1 IPA (100) 0% 40° 17-3CA-12 1 IPA (100) 6% 50° 17-4 CA-12 1 IPA (100) 18%  30° 17-5 CA-13 1IPA/water (90/10) 12%  70° 17-6 CA-13 1 IPA/EtOH/water 9% 80° (70/25/5)17-7 CA-11 1 IPA (100) 5% 55° 17-8 CA-11 1 IPA (100) 20%  60° 17-9 CA-111 IPA (100) 3% 25° (Remarks) IPA: isopropyl alcohol EtOH: ethanolSurface properties Degree of Saponi- acetyl sub- fication stitution C═O/C–C/ Contact depth at surface C–O C–O O/C P/C angle 17-1 0.20 μm 2.0 0.00.55 0.67 0.012 35° 17-2 0.33 μm 2.3 0.4 0.62 0.65 0.013 42° 17-3 0.45μm 1.9 0.3 0.46 0.70 0.008 30° 17-4 0.02 μm 2.7 0.6 0.73 0.62 0.010 54°17-5 0.07 μm 2.5 0.5 0.68 0.64 0.014 47° 17-6 0.75 μm 1.8 0.2 0.61 0.740.015 22° 17-7 0.15 μm 2.1 0.1 0.51 0.64 0.015 32° 17-8 0.008 μm  2.80.8 0.78 0.60 0.006 59° 17-9 0.90 μm 1.7 0.9 0.41 0.78 0.017 18°Adhesion Liquid crystal display Peeled Undesir- area of able bril- Ratioof anisotro- liant fogged pic layer points area (testing (sizing(storage condition) condition) condition) Viewing angle 25° C. 25° C.25° C. 25° C. 80° C. 50° C. Left- 10 60 10 60 30 30 Up- Down right % RH% RH % RH % RH days days ward ward ward 17-1 0 0 0 0 0 0 66° 36° 140°17-2 0 0 0 0 0 0 65° 34° 140° 17-3 0 0 0 0 0 0 64° 35° 140° 17-4 2 0 0 00 0 66° 35° 140° 17-5 0 0 0 0 0 0 65° 35° 142° 17-6 4 0 0 0 0 0 64° 35°139° 17-7 0 0 0 0 0 0 65° 36° 141° 17-8 15 3 23 3 11 3 61° 30° 130° 17-922 5 46 5 14 5 60° 30° 130°

EXAMPLE 18

(Preparation of Cellulose Ester Film)

A dope consisting of the following components was prepared. Eachcomponent was gradually added and stirred well in the following mixedsolvent, and left at room temperature (25° C.) for 3 hours to swell thecellulose acetate. The obtained swollen mixture was placed in a mixingtank equipped with a reflux condenser, and stirred at 50° C. todissolve.

Components of cellulose acetate solution Cellulose acetate (acetic acidcontent: 59%)  120 weight parts Triphenyl phosphate 9.36 weight partsBiphenyldiphenyl phosphate 4.68 weight parts Methylene chloride (firstsolvent)  704 weight parts Methanol (second solvent) 61.2 weight partsThe retardation-increasing agent used In Example 10 1.20 weight parts

The prepared solution (dope) was filtrated through filter paper (No.244, Azumi Filter Paper Co.) and a filter of flannel, and was then sentto a pressure-die by means of a constant-pressure gear pump. From thepressure-die, the dope was cast with a band-casting machine (effectivelength: 6 m) onto a band cooled at 0° C. so that the resultant filmafter dried and stretched might have each thickness set forth in Table8. The cast dope on the band was blown with air for 2 seconds to dryuntil the content of volatile component reached 50 wt. %. The formedfilm was peeled from the band, and stepwise dried at 100° C. for 3minutes, at 130° C. for 5 minutes and at 160° C. for 5 minutes toevaporate the solvent while let to shrink freely. When the content ofthe remaining solvent reached 1% or less, side areas inner by 15 cm fromthe edges were trimmed. Further, knurls (height: 50 μm, width: 1 cm)were provided near the edges. Thus, a non-stretched cellulose acetatefilm CA-14 (width: 1.8 m, length: 3,000 m) was prepared. The wastes ofthe film produced in the trimming were pulverized and mixed with virgincellulose acetate to reuse.

(The content of the reused cellulose acetate was 30 wt. % based on thetotal amount of cellulose acetate.)

(Longitudinal Stretching)

The prepared cellulose acetate film (CA-14) was trimmed to make thewidth 90 cm, and then brought into contact with four preheating rolls(diameter: 30 cm) heated at 50° C., 80° C., 110° C. and 130° C.successively in this order. After thus preheated, the film was sent intoa thermostat set at 130° C. The film was then stretched with a pair ofnip-rolls placed in an interval in the thermostat. Each nip-rollcomprised a stainless roller (diameter: 15 cm) coated with hard chromiumand a nipping roller (diameter: 5 cm) covered with rubber. In eachnip-roll, the film was held between these rollers to transfer. Theinterval between the nip-rolls was set so that the distance between thecenters of rolls might be 90 cm. The nip-rolls were rotated at differentspeeds so that the film might be stretched at a desired extension ratio.The prepared cellulose acetate film (CA-14) was thus stretched at eachextension ratio shown in Table 8, to prepare each film. The transferringspeed at the inlet was 8 m/minute. After stretched in the thermostat,the film was brought into contact with four cooling rolls (diameter: 30cm) heated at 110° C., 90° C., 70° C. and 50° C. successively in thisorder, to cool gradually.

(Saponification Treatment and Formation of Orientation Layer andoptically anisotropic Layer)

One surface of each prepared film was coated with 1.5 N KOH aqueoussolution (alkaline solution) in the amount of 25 ml/m², and held at 25°C. for 5 seconds to saponify. The alkaline solution was then washed awaywith flowing water for 10 seconds, and the washed surface was blown withair at 25° C. to dry. The conditions of the saponification treatmentsuch as oxygen gas concentration in the atmosphere, solvent componentsof the KOH solution, and temperature of the flowing water (washingwater) are set forth in Table 8. Thus, cellulose acetate films used forthe below-described optical compensatory sheets 18-1 to 18-5 wereprepared. The surface properties of each cellulose acetate film weremeasured, and the results are set forth in Table 8.

On the saponified surface of each prepared cellulose acetate film, anorientation layer and an optically anisotropic layer were provided inthe same manner as in Example 17. Thus, optical compensatory sheets 18-1to 18-5 were produced.

The samples for testing the adhesions of all the sheets were preparedand evaluated in the same manner as in Example 17. The results are setforth in Table 8.

(Preparation of Circularly Polarizing Plate)

All the prepared optical compensatory sheets were immersed in 1.5 N NaOHaqueous solution (55° C.) for 2 minutes, neutralized with 0.5 N sulfuricacid, washed with flowing water, and dried.

On the cellulose acetate film-side surface of each compensatory sheet, apolarizing membrane (stretched polyvinyl alcohol film adsorbing iodine)was laminated with a polyvinyl alcohol adhesive. The polarizing membranewas placed so that the transmission axis of the membrane might be at 45°to the slow axis of the compensatory sheet. Thus, a circularlypolarizing plate comprising each optical compensatory sheet wasproduced.

(Preparation of Liquid Crystal Display of Reflection Type)

A glass substrate having an ITO electrode and another glass substrateequipped with an aluminum reflective electrode having a finely roughedsurface were prepared. On the electrode of each glass substrate, apolyimide orientation layer (SE-7992, Nissan Chemical Industries Ltd.)was formed and subjected to rubbing treatment. The substrates werelaminated so that the polyimide orientation layers might face to eachother, and a spacer of 2.5 μm was inserted between the substrates. Thesubstrates were placed so that the rubbing directions of the orientationlayers might be crossed at the angle of 117°. To the gap between thesubstrates, a liquid crystal compound (MLC-6252, Merck) was injected toform a liquid crystal layer. Thus, a liquid crystal cell of TN mode(twisted angle: 63°, Δnd: 198 nm) was produced.

Each above-prepared circularly polarizing plate was laminated with anadhesive on the glass substrate having the ITO electrode, and further aprotective film having AR-treated surface was laminated thereon. Thus, aliquid crystal display of reflection type comprising each polarizingplate was prepared.

To each thus-prepared display of reflection type, voltage of a squarewave 1 kHz was applied. The display was then observed with eyes, andthereby it was confirmed that an image of neutral gray was given withoutundesirable coloring in either white mode (1.5 V) or black mode (4.5 V).Further, while the display was displaying a black image, how muchundesirable brilliant points were seen within a square with sides of 10cm was counted in a dark room. The result was shown in Table 8. Thenumber of undesirable brilliant points is preferably 3 or less, and thecompensatory sheets 18-1 to 18-3 gave no undesirable brilliant point.

The contrast ratio of reflection brightness was also measured by meansof a meter (EZ-Contrast 160D, ELDIM), and thereby it was found that thefront contrast ratio was 23.

The viewing angle giving the contrast ratio of 3 was shown in Table 8.In all the compensatory sheets 18-1 to 18-3, it was not less than 120°(up-downward) or not less than 120° (left-rightward). On the other hand,the viewing angles of the sheets 18-4 and 18-5 were approx. 60° or lessin all directions.

Before the displays were prepared, all the prepared polarizing plateswere left at 80° C. for 30 days (test for shelf life in long term).Independently, they were also left under a moderate condition, namely at50° C. for 30 days. With each polarizing plate, the liquid crystaldisplay was prepared. While each prepared display was giving a whiteimage, it was observed by the eyes to confirm how much the displayedimage was fogged. The fogs were evaluated in terms of the percent ratio(%) of fogged area based on the whole area of the image. The results areset forth in Table 8.

(Preparation of Liquid Crystal Display of Guest-Host Type)

On a glass substrate having an ITO transparent electrode, a polymersolution for forming a vertical orientation layer (LQ-1800, Hitachi-DuPont Microsystems Co., Ltd.) was applied, dried and subjected to rubbingtreatment.

The above-prepared circularly polarizing plate was laminated as a λ/4plate with an adhesive on an aluminum-deposited glass substrate(reflection board). On the λ/4 plate, a SIO layer was formed withsputtering, and further thereon an ITO transparent electrode wasprovided. Furthermore thereon, a solution of the polymer for forming avertical orientation layer (LQ-1800, Hitachi-Du Pont Microsystems Co.,Ltd.) was applied, dried and subjected to rubbing treatment at the angleof 45° to the slow axis of the λ/4 plate.

The above-prepared two substrates were laminated so that the orientationlayers might face to each other and so that the rubbing direction of theorientation layers might be anti-parallel, and a spacer of 7.6 μm wasinserted between the substrates. To the gap between the substrates, amixture consisting of 2.0 wt. % of dichromatic dye (NKX-1366, JapanPhotosensitive Dyes Co., Ltd.) and 98.0 wt. % of liquid crystal compound(ZLI-2806, Merck) was injected according to the vacuum injection method,to form a liquid crystal layer. Thus, a liquid crystal display ofguest-host type comprising each circularly polarizing plate wasprepared.

Voltage of a square wave 1 kHz was applied between the ITO electrodes ineach prepared guest-host type liquid crystal display of reflection type.The transmittances of the displays comprising the compensatory sheets18-1 to 18-3 were measured in white mode (1 V) and black mode (10 V) tofind 65% and 6%, respectively. Accordingly, the ratio of transmittances(contrast ratio) between the image in white mode (1 V) and that in blackmode (10 V) was 11:1. The viewing angle giving the contrast ratio of 2:1was measured to find 120° or more in both directions of up-down andleft-right. Further, no undesirable brilliant point was observed inimages given by the displays comprising the compensatory sheets 18-1 to18-3. On the other hand, those comprising the sheet 18-4 and 18-5 gaveimages with 23 and 36 undesirable brilliant points, respectively. Thetransmittances were also measured while the voltage was changed, andthereby it was confirmed that hysteresis did not appear in thetransmittance-voltage curve.

TABLE 8 Saponification conditions Transparent Extension Thick- OxygenTemperature of support ratio ness Solvent (wt. %) concentration washingwater 18-1 CA-14 1.5 70 μm IPA (100) 3% 60° C. 18-2 CA-14 1.4 40 μmIPA/water (90/10) 0% 40° C. 18-3 CA-14 1.6 140 μm IPA/EtOH (75/25) 6%50° C. 18-4 CA-14 1.5 70 μm IPA (100) 18%  30° C. 18-5 CA-14 1.5 70 μmIPA (100) 3% 25° C. (Remarks) IPA: isopropyl alcohol EtOH: ethanolSurface properties Saponification Degree of acetyl Contact depthsubstitution at surface C═O/C—O C—C/C—O O/C P/C angle 18-1 0.22 μm 2.00.0 0.53 0.67 0.011 36° 18-2 0.31 μm 2.2 0.4 0.60 0.64 0.013 40° 18-30.14 μm 1.9 0.3 0.48 0.69 0.009 31° 18-4 0.007 μm 2.9 0.8 0.79 0.590.005 60° 18-5 0.92 μm 1.6 0.9 0.40 0.79 0.019 16° Liquid crystaldisplay Adhesion Peeled area Circularly polarizing Undesirable Ratio ofof anisotropic layer plate (viewing angle) brilliant points fogged area(testing condition) Direction (sizing condition) (storage condition) 25°C. 25° C. Up- Left- 25° C., 25° C. 80° C. 50° C. 10% RH 60% RH downwardrightward 10% RH 60% RH 30 days 30 days 18-1 0 0 133° 122° 0 0 0 0 18-20 0 136° 120° 0 0 0 0 18-3 0 0 130° 126° 0 0 0 0 18-4 19 4  61°  55° 294 11 3 18-5 28 6  57°  60° 49 6 15 5

EXAMPLE 19

(Preparation of Optical Compensatory Sheet)

The following components were placed in a mixing tank, and then heatedand stirred to dissolve. Thus, a cellulose acetate solution wasprepared. The content of reused cellulose acetate was 30 wt. % based onthe total amount of cellulose acetate.

Components of cellulose acetate solution Cellulose acetate (acetic acidcontent: 60.9%)  100 weight parts Triphenyl phosphate (plasticizer)  7.8weight parts Biphenyldiphenyl phosphate (plasticizer)  3.9 weight partsMethylene chloride (first solvent)  300 weight parts Methanol (secondsolvent)   54 weight parts 1-Butanol   11 weight parts

In another mixing tank, 16 weight parts of the retardation-increasingagent used in Example 10, 80 weight parts of methylene chloride and 20weight parts of methanol were placed, heated and stirred to dissolve.Thus, a retardation-increasing agent solution was prepared.

The prepared retardation-increasing agent solution in the amount of 25weight parts was added to 474 weight parts of the cellulose acetatesolution, and stirred well to mix. The thus-prepared dope contained 3.5weight parts of the retardation-increasing agent based on 100 weightparts of cellulose acetate.

The prepared dope was cast onto a film-forming band. After the dope caston the band was heated at 100° C., the formed film was peeled to preparea cellulose acetate film CA-15 (width: 1.8 m, thickness: 130 μm) inwhich the solvent remained in the amount of 30 wt. %. The film was notwound up, but both ends of the film were held with chucks and laterallystretched by means of a tenter in the following manner.

First, the film was preheated in a preheating zone at 130° C. for 30seconds. The film was then laterally stretched at 130° C. for 30 secondsin the extension ratio of 1.25, and further stretched by widening thetenter so that the extension ratio might be each value shown in Table 9.Each film stretched in each extension ratio was subjected to heatingtreatment at 130° C. for 30 seconds while the tenter was narrowed sothat the extension ratio might be decreased by 2% (namely, so that thewidth of tenter might be at the extension ratio×0.98). After the filmwas released from the chucks, both sides of the film were trimmed. Thetrimmed film was then transferred by means of rolls into a drying zoneheated at 160° C., where the film was dried until the content of theremaining solvent reached 2 wt. % or less. After each side of the filmwas knurled in the same manner as in Example 17, the film was wound upinto a roll.

(Saponification Treatment and Formation of Orientation Layer andOptically Anisotropic Layer)

One surface of each prepared cellulose acetate film was coated with 1.5N KOH aqueous solution (alkaline solution) in the amount of 25 ml/m²,and held at 25° C. for 5 seconds to saponify. The alkaline solution wasthen washed away with flowing water for 10 seconds, and the washedsurface was blown with air at 25° C. to dry. The conditions of thesaponification treatment such as oxygen gas concentration in theatmosphere, solvent components of the KOH solution, and temperature ofthe flowing water (washing water) are set forth in Table 9. Thus,cellulose acetate films used for the below-described opticalcompensatory sheets 19-1 to 19-5 were prepared. The surface propertiesof each cellulose acetate film were measured, and the results are setforth in Table 9.

On the saponified surface of each prepared cellulose acetate film, anorientation layer and an optically anisotropic layer were provided inthe same manner as in Example 17. Thus, optical compensatory sheets 19-1to 19-5 were produced.

The samples for testing the adhesions of all the sheets were preparedand evaluated in the same manner as in Example 17. The results are setforth in Table 9.

(Preparation of Polarizing Plate)

All the optical compensatory sheets were immersed in 1.5 N NaOH aqueoussolution (55° C.) for 2 minutes, neutralized with 0.5 N sulfuric acid,washed with flowing water, and dried.

On the cellulose acetate film-side surface of each compensatory sheet, apolarizing membrane (stretched polyvinyl alcohol film adsorbing iodine)was laminated with a polyvinyl alcohol adhesive. The polarizing membranewas placed so that the transmission axis of the membrane might beparallel to the slow axis of the compensatory sheet. The angle betweenthe transmission axis of the membrane and the slow axis of thecompensatory sheet was 0.5° on average.

On the opposite surface of each compensatory sheet, a commerciallyavailable cellulose acetate film (Fujitac TD80UF, Fuji Photo Film Co.,Ltd.) saponified under the same conditions as those for the compensatorysheet 19-1 was laminated with the polyvinyl alcohol adhesive. Thus, apolarizing plate comprising each optical compensatory sheet wasproduced.

(Preparation of Liquid Crystal Display-1)

A pair of polarizing plates and a pair of optical compensatory sheetswere removed from a commercially available liquid crystal display(VL-1530S, Fujitsu, Ltd.), which has a liquid crystal cell comprisingvertically aligned liquid crystal molecules. In place of the removedmembers, each prepared polarizing plate was laminated on each side ofthe cell with an adhesive so that the optical compensatory sheet mightbe on the liquid crystal cell side. The polarizing plate on the observerside was placed so that the transmission axis might be in the up-downdirection, while the plate on the backlight side was placed so that thetransmission axis might be in the left-right direction. Thus, thepolarizing plates were arranged in cross-Nicol position.

With respect to each prepared liquid crystal display, the minimumviewing angle giving the contrast ratio of 10:1 in the vertical(up-downward) or horizontal (left-rightward) direction was measured bymeans of a measuring apparatus (EZ-Contrast 160D, ELDIM). The resultsare set forth in Table 9. Further, while the display was displaying ablack image, how much undesirable brilliant points were seen was countedin a dark room. The results are also set forth in Table 9.

Before the displays were prepared, all the prepared polarizing plateswere left at 80° C. for 30 days (test for shelf life in long term).Independently, they were also left under a moderate condition, namely at50° C. for 30 days. With each polarizing plate, the liquid crystaldisplay was prepared. While each prepared display was giving a whiteimage, it was observed by the eyes to confirm how much the displayedimage was fogged. The fogs were evaluated in terms of the percent ratio(%) of fogged area based on the whole area of the displayed image. Theresults are set forth in Table 9.

(Preparation of Liquid Crystal Display-2)

A pair of polarizing plates was removed from a commercially availableliquid crystal display (6E-A3, Sharp Corporation), which had a liquidcrystal cell of TN mode. In place of the removed members, each preparedpolarizing plate was laminated on each side (each of the backlight sideand the observer side) of the cell with an adhesive so that the opticalcompensatory sheet might be on the liquid crystal cell side. Thepolarizing plates were arranged (in O mode) so that the transmissionaxis of the plate on the observer side might be perpendicular to that ofthe plate on the backlight side.

With respect to each prepared liquid crystal display, the minimumviewing angle giving the contrast ratio of 10:1 in the vertical(up-downward) or horizontal (left-rightward) direction was measured bymeans of a measuring apparatus (EZ-Contrast 160D, ELDIM). The resultsare set forth in Table 9. Further, while the display was displaying ablack image, how much undesirable brilliant points were seen was countedin a dark room. The results are also set forth in Table 9.

Before the displays were prepared, all the prepared polarizing plateswere left at 80° C. for 30 days (test for shelf life in long term).Independently, they were also left under a moderate condition, namely at50° C. for 30 days. With each polarizing plate, the liquid crystaldisplay was prepared. While each prepared display was giving a whiteimage, it was observed by the eyes to confirm how much the displayedimage was fogged. The fogs were evaluated in terms of the percent ratio(%) of fogged area based on the whole area of the displayed image. Theresults are set forth in Table 9.

[Evaluation of Unevenness of Displaying]

Images given by the liquid crystal displays prepared in Examples 17 to19 were observed with the eyes. As a result, no unevenness caused by theroughness of the film was observed, and thereby it was confirmed thatthe optical compensatory sheets of the invention had enough smoothsurfaces to be used in liquid crystal displays.

TABLE 9 Saponification condition Surface properties Trans- Exten- OxygenTemperature Degree of parent sion Solvent concen- of washingSaponification substitution C═O/ C—C/ Contact support ratio (weight %)tration water depth at surface C—O C—O O/C P/C angle 19-1 CA-15 1.22 IPA(100) 2% 55° C. 0.14 μm 2.1 0.0 0.55 0.66 0.011 36° 19-2 CA-15 1.15IPA/water 0% 45° C. 0.26 μm 2.2 0.2 0.60 0.63 0.013 44° (95/5) 19-3CA-15 1.30 IPA/EtOH/ 4% 60° C. 0.21 μm 1.8 0.1 0.49 0.70 0.008 30° water(80/15/5) 19-4 CA-15 1.22 IPA (100) 21%  60° C. 0.006 μm 2.9 0.9 0.810.59 0.005 61° 19-5 CA-15 1.22 IPA (100) 3% 18° C. 0.98 μm 1.5 0.8 0.370.80 0.019 16° (Remarks) IPA: isopropyl alcohol EtOH: ethanol AdhesionLiquid crystal display-1 Liquid crystal display-2 Peeled area ofUndesirable Ratio of Undesirable anisotropic layer brilliant pointsfogged area brilliant points Fogs (testing condition) (sizing condition)(storage condition) Sizing condition Storing condition 25° C. 25° C. 25°C. 25° C. 80° C. 50° C. Viewing 25° C., 25° C., 80° C., 50° C., Viewing10% RH 60% RH 10% RH 60% RH 30 days 30 days angle 10% RH 60% RH 30 days30 days angle 19-1 0 0 0 0 0 0 158° 0 0 0 0 100° 19-2 0 0 0 0 0 0 162° 00 0 0 110° 19-3 0 0 0 0 0 0 155° 0 0 0 0 105° 19-4 19 3 22 3 16 3  79°28 4 12 2  70° 19-5 29 4 42 4 14 3  77° 40 5 16 3  65°

1. A process for preparation of an optical compensatory sheet comprisinga cellulose ester film, an orientation layer and an opticallyanisotropic layer formed of liquid crystal molecules in this order,alignment of said liquid crystal molecules being fixed, wherein theprocess successively comprises the steps of: coating an alkalinesolution selectively on only a surface of the cellulose ester film onwhich the orientation layer is to be provided, wherein the alkalinesolution comprises a solvent comprising an alcohol, and wherein theamount of water contained in the solvent is 0 to 15 wt. %; washing thesurface to remove the alkaline solution; coating a coating solution ofthe orientation layer on the washed surface; drying the coating solutionto form the orientation layer; forming the optically anisotropic layercomprising the liquid crystal molecules; and fixing alignment of theliquid crystal molecules.
 2. The process as defined in claim 1, whereinthe alkaline solution is coated on the surface under an atmosphere inwhich concentration of oxygen is 18% or less.
 3. The process as definedin claim 1, wherein the surface is washed with water heated at 30 to 80°C.
 4. The process as defined in claim 1, wherein the alcohol isisopropanol.
 5. The process as defined in claim 1, wherein the alkalinesolution is coated to form a saponified surface having a depth ofsaponification in the range of 0.01 to 0.8 μm.